Here is mine, in no particular order:
Expanded campaign. If they wanna keep it online only, that's fine. But make it more than a brief conversation before a match starts and some mid-match dialogue. There is TONS of potential with this IP for an awesome story. Watching MacAllan lead us into battle in his Titan, what he does at the end of the campaign, the space skirmish and pod drop before The Battle of Demeter, all incredible moments that probably eclipse anything I've played in a shooter since MW2, except for maybe shooters with no MP at all and a sheer SP focus. They could do so much.
Customizable Titans. Just visual stuff. Would be amazing. Maybe even allow us to design our own shit like Forza? How awesome would that be? I wanna charge into battle in my Denver Broncos John Elway #7 Titan. Hell, I would have Elway for my Atlas, Trevor Pryce for my Ogre, and maybe Baybay for my Stryder.
I would love more strategic modes. I think due to time constraints they just scratched the surface of the potential here. Imagine the Demolition they brought into MW2 only Titanfall style. Or some type of Rush style mode where destroying one section opens up another.
That's all I need on top of the typical new weapons and gadgets and abilities.
I saw someone mention it but I hope they don't do bullet penetration or destruction. It's one of the things that gives the game perfect balance imho. You have the sheer firepower and strength of the Titans in a finely tuned battle against the agility and quickness of the Pilots. It might suck to see shooting a Pilot and see him run into a building where you might not be able to get him, but the game needs that escape factor. It's what makes it intense. I mean imagine Training Ground or The Colony where all the buildings are gone. If you don't have a Titan, you're fucked.