Logical change, well done.

Besides being more realistic, we think that this will also result in fewer raids of small players as even a small player will have the opportunity to do some damage to the attacker, who in turn would have to consider wisely if it makes sense to raid a planet.

Really small players often can't even build a single explorer, because they are getting attacked all the time. That means they can't start really playing the game at all.

I think a rule would help that one cannot attack a certain planet more often than once a week.
Furthermore I suggest it should be possible to stop producing, so even if a small player cannot win a battle, he could then prevent the attacker to gain a lot of resources.