Lower GP should win if tied in GAC.

Nah. Nothing should ever discourage roster growth.

The person with more invested should win the tie breaker. It’s fine the way it is now 

Many players agree, but that's not how CG gets people to spend time, money, and resources on their rosters.  Especially money.  If you were rewarded for a smaller roster, people would debilitate their own rosters to make them smaller.  (Just like the way it was in previous GACs where people hyper focused to have smaller rosters to face smaller opponents.)

They need to do a lot of fixes to GAC and TW though.  At the same time, there are players in K1 who have smaller rosters doing the "efficiency" match where they pretty much ignore defense and go for the high score by saving everything for offense.  (I call it the wuss defense, but efficiency strategy sounds nicer I guess.)  In that case, even more players would go full offense and ignore defense, then get rewarded for it by playing only half the match.

I have a bloated, inefficient roster (9.3 million GP) that is under GL'd (only got 3), under Relic'd (most between 3-5), under Shipped (1 GL capital ship) in almost every match (K3) I am in. I would love a tie breaker in favour of a smaller GP, even though it would not benefit me.