Shall we talk about the cons?
Grifball - No major difference to Halos 3 and Reach except that it uses Oddball gametype
Ordinance - Can't really promote camping since most weapons offers are completely random, Knowing where Power weapons spawn is usually the cause of camping to most games, especially Rocket Launcher spawns
Loadouts - Not really unfair, its mostly seen to be customized to a style he/she is more comfortable with (Plus Don't really see a big difference to all the loadout weapons)
Skins - All armour has one skin (Recruit is a possible two due to LE owners), it'd be a waste
The Mantis - It's slow movement and bulkiness (making it a big target) compensates. Plus It's a dumb move to take it head on without being prepared, simple as that
Race, Multi team - Can get that through Custom games no problem, and if most Reach gametype return, it would be a case of it coming back to Matchmaking (Unsure about race, but possible)
Invasion - Bit hard when we can not play as Elites, plus Requiem is still a unknown to both humanity and Convanent
((Can't make Forge comments due to not using yet))
Initial Spawns - Looked more balanced than said.
Legendary Ending - Would've been seen sooner or later