There is a lot to say here... but I'll try to be brief.
Sensors/etc. is yet another element that could be handled better if Influence and Borders were two different things. Hard borders created by your planets and assets that don't continually expand, could certainly have "free vision" without causing nearly so much disruption. Influence can truly become massive. There are other issues with "Influence as a border" that are discussed elsewhere at great length.
The new surrender mechanic. Since surrender in GC has always been intended as a way to speed up the end-game, it's not terrible that it just destroys all the planets/etc. BUT it is a missed opportunity to take surrender more seriously.
1) Personality type could influence the type of surrender and to whom. (With some empires electing to blow everything up, and others offering you direct control, and yet others declaring all their planets independent, etc.)
2) Big morale penalties could come from a surrender.
3) Option to install "vichy" government, that, is akin to a commonwealth for the next 50-100 turns, but then becomes a truly independent faction again.
So point is... there are plenty of opportunities to improve surrender mechanics, but only if it's seen as something more than a late game wrapping up mechanic.