#2 sounds great. Size is the only ship constant I can think of, and we need default symbols, period. #1 is a bad idea: lets keep complexity away from the average player as much as possible unless it's
really important, like race or galaxy set up. I have a slightly more
KISS idea that could work.
Everything else changes too much, so unfortunately I can't see roles being interpreted with any reliability.
Here's what I think the symbols need to do:
1: (Empire) Color should represent the side a ship is on.
2: Symbols should simplistically, clearly distinguish between 6 different sizes which are........ Actually I'm not sure exactly what they are, but they'll need to. (are fighters a ship size?) Simply expanding a single dot isn't good enough, because there are 6 phases it would have to go through.
3: Different shapes represent roles, but I have no idea what roles could be. We should find other games that tackle this problem.
So here's the KISS idea: Remember space Empire and MoO3 forced the user to categorize all their ships? Every ship fell into a distinct category; it was either an attack ship, or a carrier, or a transport or a missile boat, so my thought is why don't we force ship classification? Then we can assign icons to designated ship classes.
So here's 4 classes, and they could have an icon:
Small ship design} ____ Point defender (Small)
> ____ Battleship (Small)
x ____ Missile Ship (Small)
o ____ Carrier (Small)
And when you change to a larger or smaller hull, the icon changes (somehow) accordingly to represent that:
Large ship design}} ____ Point defender (Large)
<> ____ Battleship (Large)
X ____ Missile Ship (Large)
(O) ____ Carrier (Large)
Enemies (automatically taken care of)
Radar map}} ____ Point defender (Large)
<||> ____ Battleship (Absolutely Gargantuan)
X ____ Missile Ship (Large)
o ____ Carrier (Small)
The design screen should list the respective icon next to the classification for ease of use.
This all reminds me of emoticons

(I hope you won't mind tweaking the ship design UI)