Listed in order of importance, dev decisions here,
META: Nail down a meta, and direction for Hawken. Choices; sticking with what we have now, which is more Arena esque with some mechy mechanics and style (very quick, darty, lowish TTK). Or pulling the arena bits back a smidgen to provide a more mechy-sim-esque vibe with arena style combat sprinkling (a hair slower, less spammy, less darty perhaps, slightly higher TTK) . And most importantly, please just stick to whatever you decide to go with.
Balance: Once that's in place and rolling, balance the hell out of the individual mechs, items, internals, and classes within that meta.
Content: Start cranking out maps, lots of map if possible, if possible, adjust current maps for the meta. Followed with new mechs, and mech swag. With new mech swag coming out, please consider limiting mech parts to only that particular mech chassis. Not sure if the current system which enables a Predator to look like a CRT is the best idea (just one example). Yes you CAN, and SHOULD, be looking at a mechs weapons or icon during an engagement, but the first this you typically (naturally) look for is a mechs shape or appearance during that quick skirmish which decides your engagement tactics. The current setup enables disguising mechs which can be off putting or confusing, at least for me it is. I can only imagine what a new player thinks when an Assault or CRT goes invisible.
Leader boards / clans / Rank system: So you have the content to get people to play, now give them a reason to stay. Chasing rank, climbing the leader boards, and in game community. Adjust the ranking system to avoid the MMR chasing, Titanfall's rank chip comes to mind which I feel is a really neat approach to "rank". The "rank chip" idea doesn't need to be copied exactly, but it;s a nice way to avoid having to split up servers for ranked and unranked matches. When you want to chase rank, activate the rank chip, if you want to relax, turn the rank chip off. Over time though your rank chip degrades if not actively playing. Keep MMR hidden, leave it as a MM tool exclusively, not something that players actively chase to increase. Clans, obvious reasons.
Audio / Visual: At this point if things are going well, maybe consider tweaking the audio / visuals. It's been a few years since the game launched, video card prices have come down, maybe it's a good time to spruce things up a bit. Get Hawken caught up with the times. I'm not suggesting Hawken isn't already visually impressive, but a little more bling is never a bad idea. Bring back that griddier tone to maps, more smoke effects, projectile trails with smoke etc etc. Audibly Hawken could use a bit of tweaking, maybe even some regression back to how a few things sounded early on. I mean what the heck happened to the Vulcan? It used to have a weight to it, now it sounds like a pea shooter. Many times I find myself wishing some sounds had more weight to them. Would be cool to have bullets, missiles, or grenades have a "wizzing by you" sound. Could be exciting to dodge a giant tow, and hear it scream by your mech, and explode behind you.
EXTRAS: In theory at this point the game is healthy, and sustainable. Optimistically a little over a year out at this point in my fantasy. I'd like some type of single player DLC. A nice 6-7hr campaign, $14.99, to let players explore the lore, and it could fill that sim mech experience a lot of mech fans crave, myself included.
I didn't include any server, or code tweaks in my run down. I don't fully understand the extent of that work, but I'd imagine going through Hawken's code is something that is actively happening now and needs to be done before anything substantial can happen. Same goes for the servers, which it seems like is also happening now.
But yeah, that is what should happen in my dream world. I'm not a game dev, so I have no idea how realistic anything I've rambled on about is. Be gentle people.