Considering IllFonic's last game gave players the ability to unlock different Jasons from different Friday the 13th movies, even the futuristic Jason X, I think it's reasonable to assume players will be able to unlock various Predators.
2, True voice chat and Proximity Chat: In Halo 2 and 3, only players on your team could hear your voice at all times while in-game (except for pre-game lobbies, where everyone can communicate freely). However, there was a feature called Proximity Chat that let you and enemy players hear each other if you were close enough. If Hunting Grounds had this feature, perhaps Vocal Mimicry could allow the Predator player to record the actual dialogue being spoken between team mates that he can overhear while stalking them nearby, and throw it back at them (with the distortion effect applied) as a taunt mechanic? The obvious downside is, given the usual vulgarity and immaturity of online gaming, the Predator player could inadvertently mimic some really questionable or offensive stuff.
Wow! Very creative!
It's not likely to be implemented for reasons already stated but that would truly be something special. Nice idea!
Friday the 13th had proximity voice chat that led to some very fun situations, so I wouldn't be surprised if it showed up here too, though yeah obviously without actually being able to record it.
That mud camouflage idea is cool, it could definitely help give the humans an edge, though you should probably only be able do it once at one spot. Otherwise it wouldn't take long for the thermal vision to be rendered useless if every match turned into a race to the mud spots and the entire human team could just camo themselves.
I'd also like it if you could string bodies up, even if only at certain predetermined spots like in Concrete Jungle, which would give you bonus "trophy" XP as the Predator but leave you vulnerable while you were doing it. It'd give you a reason to do it, but also come with a downside that the human players could exploit if they caught you doing it, or saw one of their fellow players strung up and realised that was something you were trying to do.
And yeah as has already been mentioned, the Predator as a character has a lot more variety in terms of what he can do than Jason does, so I wonder whether they're going to go with a pre-set list of stats/attributes like with Friday the 13th or have more of a customisable loadout for him? You could do cool things with either I think, like have a pre-set Predator that focuses on melee with no ranged weapons, one that's all about range but not got a lot up-close, one that perhaps has the medkit so he can heal/regain health but with the trade-off of not having as many weapons as other Preds etc.
Likewise if they went with a player-custimisable loadout they could possibly go with a points or slots-based system, where each item you could equip would take up a certain amount of space in your loadout, so that you could have one or two powerful items at the cost of others. You could either go with one big, powerful weapon or gadget and not a lot else, or try to balance things out with multiple items that cost less in points or slot space.
Either way Illfonic definitely did good with the multiple Jasons fan service in Friday the 13th, so it's a pretty good bet that whatever system they're going with we'll be getting multiple different Predators to play as.