As far as Graphic-quality/performance goes:
-Need level of detail controls
-Dynamic Shadows
-DirectX11 support
-dynamic loading sequence for textures and meshes (like how in CoD I've noticed on low-ram PC's, it loads very low-res textures and slowly fades in the high-res textures once fully-loaded) which would allow for a lot more guns and entities in a level, because they only load when needed.
-REAL-TIME EDITING! NO MORE WAITING TO COMPILE XP
As far as others features go:
-Multiplayer with dynamic entities (of course), optional stuff like leaderboards and lobbies, friendslists, etc. And Developers should be allowed to add in their own plugins (maybe even to make it scompatible with steam even?)
-Weapon attachment-system / Custom-Loadout System
I'd like to see Player hands as a separate mesh than the Guns themselves, so different characters or outfits have different meshes. For attachments, I'd LOVE to see a rail-based system, where gun meshes have rail-spots (under-barrel, barrel, optic rail, alternate-magazine options) so the different attachments would be simply be variables that determine if/what attachments are on that gun (with the attachments as a set of global meshes that can go on any gun the developer chooses)
-Lastly, The Player Camera needs improving. Developers (and Players) should have instantaneous control over FOV. options for standing, crouching, and PRONE should be available, with custom heights if the developer chooses. I think the option to have camera-shake (like when running, explosions, etc.) really add to the depth and immersion of players into games like Battlefield 3.
Regardless, I'm very excited for FPSC Reloaded, despite I do my serious development with Unity and other engines, I'd love to see the Ease of use of FPSC finally cross-roads with the features it's deserved for years. And who knows, with the release of Windows 8, I'm sure a much larger market of Low-end PC Gamers will come into the equation.
My Craptop's Specs: Windows 7 Ultimate; AMD sempron 2.1 GHz single-core CPU; ATI radeon 3100 non-HD 256mb dedicated, up to 1.5 GB total; 3 GB DDR2 333 MHz RAM
Screen Resolution: 1280 x 800