I've thought of a way to defend bases, not overpowering them, and getting a reward for successfully doing so:
Every defending member can contribute energy to base defence.
This energy is logged in a contribution table.
For every X energy contributed, a SINGLE CHOSEN BASE STAT is increased by a fixed %. This could be shield/hull capacity, attack, or defence.
The effect ends after the lock is lost.
If the base is defended, the "top contributors" get gold badges in the same way that attackers would have got silver badges (eg top 1-5 get 2, 6-20 get 1 for a lvl2 defence).

This could work well because:
Level <4 bases could now have a chance against bigger legions.
Bigger bases, which are less likely to be targeted, get higher gold badge rewards.

Also the cost to increase a stat by 1% could scale with base level, making things fairer.

Also, on another note, after base level 4, the max silver badge payouts should increase, something like lvl5 = 7, lvl6 = 10, lvl7 = 15, reflective of the scaling difficulty.

What if you get badges based on the the attacking legion's base level