My combination of suggestions

Combination of ideas (I've tried to say who's but if I've missed anyone please say)

Main purpose is to balance the game but without making those that have invested well already lose out.

Artifact tech to stay but stay low, artifact drop to stay rare.

Relays:

Scrap the relays entirely as they stand and replace with vevos idea of a homeworld bonus system with a few additions or adjustments.

Replace the relay with an alliance planet that every alliance gets. You are allowed to place them wherever you want when you create the alliance.
You can build special buildings on the planet that increase the stats of all member. These will include a buildings each for carbon/chips/hydro/energy. Cap the bonus limit to 100%
Start level is 5% bonus, upgrades are with ress only, increasing ress per 5% upgrade, growth is similar to current infra growth.
One further building available to use only if all 4 other building are producing a minimum 50% bonus will be a communications post able to detect incoming attack fleets against any alliance member planet in the same galaxy or the relay itself. (not sure if possible but I like the idea)

You can build def there and send ships there (as currently done) to protect the planet. Whenever you lose a fight you lose a building on the planet (random) and the building reverts back to 5% start point. You will the. Obviously lose then communication post

Any ships sent to defend the homeworld are like any other planet defence and can be recalled. Any member of the alliance can upgrade the buildings with ress but only by the exact amount, no pooling until done.

Create an intercept fleet option.

If an attacking fleet towards the homeworld is detected by the homeworld communications post the alliance is given the chance to send its defensive fleet to intercept, this battle will take place on an empty planet near the homeworld meaning no building damage.
If an attacking fleet towards a players planet is detected by the communications post an intercept chance is given and as above if successful will take place on an empty planet
Replace the last branch of the ship skill tree with an intercept success skill
The chance of launch is a random one that has an increase in success if the player (or alliance average) has a high ship tree intercept skill.

Ranking.

Leaderboard to change to 3 part.

1 Miner for mining stats (current level leaderboard)
2 Warrior for current ships board
3 Overall combines both into 1 rank, would be calculated by ((miner/3) + warrior)/2
This should make the more warrior style players jump up the leaderboard and the miner type drop down.

(I have done this to prioritise pvp battle within the game)

Player protection to stay in place on all overall rank under 100. No protection on overall rank 100+

Timos idea (slightly adjusted) to be used on all players

Delete the fleet limit per flight and the 70% limit stealing rss, replace it for a total fleet point limit (for every player the same) limit is shared across all planets
Total fleet point limit should include defense (the more defense u build, which is stronger as fleet, the less fleet u can build)
Earn scrap points for every ressource u steal from active enemy players

What will happen?
- offensive players (fleeter) will get more scrap points if they attack miners
- miners will get robbed totaly until the fleeter is out of scrap point range
- if miner decide he want to stay that low, he needs to live with it, that every fleeter will rob him until he have to high scrapscore
- if miner decide to deff he will earn scrapscore too and rank up
- mining isnt op anymore, wow u have more rss to build more ships but u cant build more ships because its limited
- fleeter got stronger ships but need to farm other to get the rss for it
- it will regulate itself this way

My idea to be combined with new leaderboard

Keep scrap point calculations the same during a a battle but losing player does not gain those points but has to give winning player the scrap point as a tribute, losing them off his own score. This means a stronger players losing battle can actually drop in the warrrior leaderboard and be replaced and consequently the overall one, having to earn their way back to the top with more battles.

Group attack scrap points as per sof suggestions

Distribute scrap and scrap points from group attacks (for example 50% to main attacker, 50% distributed among rest. Thought for uneven distribution is to have more profit for the fleet skill. So they have its reward for not going infra skill.)

Spying changes as per sof suggestions (adjusted slightly)

Add a way for player with lower spy lvl to get intel from ppl with much higher spy lvl, For example send more probes for higher chance of  getting intel.
  Used probes are destroyed or have a chance to be destroyed
  i would suggest 1 probe +0 (0% chance of destroyed)
  10 probes +1 (15% chance of getting detected)
  100 probes +2 (30% chance of getting detected)
  1000 probes+3 (45% chance of getting detected)
  ....
  if detected 50-100% random are destroyed

Updated change to ranking system

Ranking.

Leaderboard to change to 3 part.

1 Miner for mining stats (current level leaderboard)
2 Warrior for current ships board
3 Overall combines both into 1 rank, would be calculated by ((miner/3) + warrior)/2
This should make the more warrior style players jump up the leaderboard and the miner type drop down.

Make it a sliding scale if influence on the miner side to make sure miners who don't get any scrap score can't make it to high without going over 100 overall.

Make it so that even if a players ghosts while being attacked his buildings take a hit from the attacking fleet and 1 random building would go down a level and scrap score is generated for both players, this way miners ghosting can't be seen to not add any scrap score.

Player protection to stay in place on all overall rank under 100 but in the following way

For overall rank under 100

Fleet limit cap is still active for attacks on player under level 100 by those above 100. Same is true for group attacks.
Delete the current fleet limit per flight and the 70% limit stealing rss, replace it for a total fleet point limit (for every player the same) limit is shared across all planets
Total fleet point limit should include defense (the more defense u build, which is stronger as fleet, the less fleet u can build)
Earn scrap points for every ressource u steal from active enemy players

Above overall level 100 only changes would be no fleet point limit at all.
Group attacks against anyone over level 100 can include all players above or below level 100

Keep scrap point calculations the same during a a battle but losing player does not gain those points but has to give winning player the scrap point as a tribute, losing them off his own score. This means a stronger players losing battle can actually drop in the warrrior leaderboard and be replaced and consequently the overall one, having to earn their way back to the top with more battles.