[This space intentionally left blank]
Some interesting changes you are proposing. I'd be hesitant to change the fundamental balance that much, but modifying the game to make it more fun to you is always encouraged by the designer.
This will seriously nerf both fighters and raiders. Level one fighters will now only have a chance of 30% to hit a colony, 40% if they have attack 1. This means that even a full CV will only land an average of 1.4 (0.2+3*0.4) hits. That means they will usually have to stay over a colony for an entire round to destroy it. An early game raider rush has the same problem.
5.10 Colonies & Combat
The calculated “To hit” number is reduced by two if attacked by a hull size of 1 (eg, SC, DD, F, SW); it is reduced by one if attacked by a hull size of 2 (eg, CA, BC, R).
Since hit and run is the name of the game (for raiders more than for fighters) I'd be hesitant to implement this.
Maybe have hull 2 have a zero modifier (hull 1 = -1, hull 3 = +1) and give fleet size bonus if there are more than 5 ships. Still makes it harder for a single CV, but two will be able to take down a planet even after losing a couple fighters.
This might make it too easy to destroy colonies in the late game though.
Large swarms are already heavily penalized late game for two reasons:
The intent of the 5.5 rule change is have a more graduated change to %-age at the low end of the "to hit" scale, without eliminating the possibility of a "Luke, use the force!" lucky hit. Comparison of %-ages before/after are:
-1 or less...10%.....5%
To retain the game balance, the small increase in %age at a "to hit" of 1 is balanced by an (almost) equal decrease in %age at a "to hit" of 0. Both are still about 10%, in big round number terms. So I hope to not affect game balance too much by this change.
There is a larger change when the "to hit" is -1 or less, but this occurs less frequently. An example might be SC+1 vs BB+3 or DN+2. So this rule change might affect a late game SC swarm versus large capital ships. However my thinking is that (1) the large capital ships would be accompanied by other vessels which would be targeted by the SCs first; and (2) I find it unsatisfying that under current rules a SC+1 has the same chance as a DD+1 or a CA+1 against a BB+3/DN+2.
1) They fire later than big ships.
2) They have less hull points.
Combine those two and you already have abysmal odds for a scout swarm vs BBs.
Basically the ships that you might currently use to get a fleet size bonus and a 10-20% chance for a hit would then become only relevant for the fleet size bonus.
An early attack is already penalized since you have to brave the dangers of deep space without exploration technology. If I can't build a fleet to defeat whatever makes it through I should lose the game. If that makes the game too quick just play two games in a row
The intent of the 5.5 rule change was to reduce the devastation of an early attack by low budget forces. It reinforces the idea of large capital ships as "planet busters". Smaller vessels (even single ones) can still blockade as per current rules, denying the economy to enemy, but take longer to reduce entire colonies.