Allow in gal attacks, but dont give an eta 5 travel time... raise it to the normal one. Otherwise whenever someone in your gal got incs, you could flood the attack with value and completly screw the attackers cap (keeping the roids in gal that can then be farmed back)
I think a good way to alter the exile system is to allow galaxies to offer spots for sale, and potential exiles can then pay an increasing amount based on the quality of the galaxy.
For example, the cost to exile into a particular galaxy could cost 1 resource per galaxy value or similar, you can then save up to try get into the top gals. This would mean that only big planets could afford to go into the big gals, so possibly there could be another cost? maybe loss of constructions? Each galaxy could set a cost to join, with crap gals obviously free to join, and bigger gals more expensive. The amount spent could then be donated evenly to each planet in the gal they are exiling from.
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Extreme Q