I saw this idea a while back and to be hones I was thinking of something similar. Please note that the suggestion is an actual working system in different game I used to play (I am not sure I am allowed to say the name so I will keep it to myself for now). Here is the original topic: viewtopic.php?f=45&t=9341

Now I would like to explain how the system was working in the other game and cover the diferences in here and what I think can be used in order to make things work for us. Please note that implementing PVE, something we never had before is going to disbalance the game as you say, but also stimulate players to be more active.This is going to be an extra income and it is still going to be higher profit for the higher ranked players, but also an opportunity for the lower rank players to have some fun while growing.

I. Discovery
First I want to start with the findings - In the other game the those were the main source of income for players. Note that those pirate planets are not going to be visible until you send a special unit called explorer to each individual spot in the system in order to find one pirate planet. Now those take time and slots and this is not the best solution for our game. There are 3 possible ways to work around it.

1. Make all pirate planets visible - this way we can just go quickly trough the galaxy and have them all spot on. The lazy way we can have - just spy and fly.

2. Make a special exploration unit. On the other game there were a lot of slots due to the exploration factor, but for us this is not going to be the same. Instad we can have a special unit (exploration probe), that is a 1 time deal - it is going to fly fast in the galaxy going either upwards or downwords from your current location until it finds an unknow pirate planet. Once the planet is found you can spy in in order to see what there is. Upon discovery the exploration probe is destroyed - pirates like to have target practive on those.
Note: This is probably the most complicated approach. I am just giving it as an example so there could be a bigger variety of opportunities for the suggestion.
3. Add a new discovery function into the game for the lanx. It's simple and it can work like the jump gate - click on the lanx and it will open the discovery panel. Pay a small deu fee to find the closest pirate planet. Pirate planets can be of any level that you are able to see. (My personal favourite option)
Pros and cons:
Now it's obvious that moons for lower level players are hard to get. That makes the level 1 pirate planets hard to discover for new players. There are 2 things to be considered here - higher level players can "Announce" level 1 pirate planets to a new player. Ofc, that will require the level 1 player to ask for it. Therefore I would suggest level 1 pirate planets to be visible by default so the new players can easily see them on the map and that to spark up their interest.

Discovery note - in case the options 2 and 3 are liked and approved the discovery of the pirate planets works like that - a player within certain ammount of points is able to attack a specific level. The discovery will be current level+1. So if I am within the level 2 pirate planets attack range than I can discover up to level 3, but level 4 and 5 will be invisible for me.

II. Rewards
Based on the other game the rewards for level 1 and 2 pirate planets should be containing mainly metal and crystal. Level 3+ should start containing a fairly big numbers of fuel as the fleets that are going to be flying for them are going to be with large sizes. Now on the other game most of the time the pirate planets would of contained 1 zorg ruby (the payment currency). Now there is a big difference in the ammount of payment currency that can be spend here and in the other game so I would suggest a new currency to be added - zorg ruby shard. Collecting (for example) 15 zorg ruby shard will give you the opportunity to craft them to a zorg ruby. There is also the possibility to keep zorg ruby shards as a new currency and work on a special shop for items that can be bougt with those (If you like the shop idea let me know and I will work something out, I already have considered a few posibilities.)

III. Spawns
Now this is a hard one. In the game I am using as a base on this there are 63 slots on the map (compared to our 15 in galaxy) and on one map at all times has 5 to 7 pirate planets. Meaning pretty much if you kill one there is instantly spawning a new one on its place that you need to discover. However the count of those doesn't mean that you can kill them all. That was a problem for the other game too - there was a necesity of lower rank players to clear the lower level pirates in order to keep the number the same and to spawn higher level pirate planets on it's place (ofc the new one that spawns will be a random level). A solution for the game was to add an option to pay the equivalent of 200 zorg rubies (or zorg ruby shards as I suggested to be changed) and be able to attack all levels of pirate planets for the next 6 hours in order for new ones to respawn nearby. Now this is something that I like and can be used, but note that the TTL (time to live) for one pirate planet over there was 15 to 20 days. Our servers are not that populated and having 5 different levels of pirate planets cant be painful. So far in my head the best spawn solution would look like this:

1. A spawn of 1 pirate planet every 3 systems (1-3, 4-6, 7-9 etc), which makes it a total of 100 pirate planets in a galaxy or 900 over the 9 galaxies divided by 5 different levels. On avarage that makes 180 vaiable choices for a player in the entire universe.
2. Once a pirate planet is destroyed there will be an instant respawn of a new pirate planet within the 3 system range.
3. Every pirate planet needs to have a short TTL (time to live). As I said, the player base is low and can't cover all 5 ranges at all times. Examples: 18 to 24h, 24 to 30h, 18 to 30h, where the exact time is randomly generated between the 2 peaks
4. All pirate planets spaw with random level. OR!
5. After the TTL of 1 pirate planet has expired and no one kills it it gains an additional level. If the pirate planet is level 5 than a new random spawn will appear.
6. The TTL of a pirate planet should not be visible. However since it takes time for us to get there it will be a waste if a level 5 dissapears before the destination is reached. Therefore a good solution will be to add 3 TTL states of such planets:
Unknown - 1h+ hours before respawn/upgrade
Short - 30m to 1h before respawn/upgrade
Very short - less than 30m before respawn/upgrade

IV. Limits
I cannot predict those yet unfortunately. This is still just a general idea to what we could work on. As you see I talk about the system in general, but not with exact numbers of what fleet the pirate planets are going to have or reward numbers. The way I see things in my head I think that the system I am offering is pretty decent and could work without limitations as long as you are consistent with it. I would like to mention however that in the game I am using as a base for this there was a limit - you cannot attack more than 30 pirate planets within 24h period from one another (i. e. if the first attack occurs in 12:34 than the 31st attack cannot occur before 12:34 on the next day). Exception: If the option for 200 zorg ruby shards to attack all levels for 6 hours is used as mentioned before than for those 6 hours there is no limits! After the 6h have expire the count resets to 0.

V. Final notes
I am pretty sure that there are things that I have missed to discuss, but right now I am typing this down spot on. I did not take my time to work on this suggestion over a few days or a week - I would like to see some feedback first, but I am ready to put more time in developing the basics with your help. Let me know what you think and how you feel about it.

Zorg recently said that we can rework old suggestions so here I am. I really would like to contribute to the game evolution and I am ready to work on other suggestions too. If you guys like the idea of zorg ruby shards and a shop for them I have something in mind for that as well and I can write a separate topic for it. I also have another suggestion about quest/achievement system that I am going to be releasing shortly and the zorg ruby shards could fit perfectly into it as well.