That's not the "only" reason: In my case, and in the case of a lot of the folks that I've played and grouped with, it's an alternative to the Piranha at 20 tons for putting Faction Play drop decks together. Even more importantly, the Firemoth was THE de-facto scout 'mech for Clan Ghost Bear. The Ghost Bears didn't use the Piranha, nor the Arctic Cheetah, and had a fair few fewer Mist Lynx' than they had Firemoths. In order to more accurately role play as a member of Clan Ghost Bear, we need the Firemoth. The other main reason is the only reason to get more than 30 or 40 'mechs: Pokémech. "Gotta catch 'em all".
Now, now: be nice to the Adder. The REAL first good-looking Clan Light.
Otherwise, yes: the Fire Falcon would be a good addition at 25 tons, and would be an alternative to the Mist Lynx for Clan Jade Falcon drop decks.
This sounds completely reasonable, and along the lines of what the staff at PGI have proposed in the past, right before being pressured into giving us all more, faster. Better to get something at a reasonable pace, than not get anything at all.
On the one hand, I want HAGs because we have a lot of missing variants that are only missing because of that weapon system (going back to Pokémech). On the other hand, power creep is getting so far out of whack that we'll need to think long and hard about how best to implement them.
My own suggestions for new 'mechs to add (though I feel like there should be a "add your own" vote system pinned to the top of this thread, and whenever PGI shuts down the vote, the highest votes win), starting with tonnages that only have a single option:
Firemoth (CL, 20t)
Fire Falcon (CL, 25t)
Mongoose (IS, 25t)
Turkina (CL, 95t)
Other 'mechs that I want for Ghost Bear roleplay:
Kingfisher
Grizzly
Or for reliving the MW4 glory days:
Stone Rhino (Mektek mod)
Longbow
Obviously, insofar as the "Pokémech" concept or fleshing out the universe feel, adding the remaining Unseens and the rest of TRO 3025 is desirable, as is adding Tanks, Aerospace, and Infantry to flesh out the combat experience, even if non-mech assets are only AI controlled. (Wasn't there some concept back in the day about units who got their tag on a planet being able to purchase upgrades for the defense of that planet? Back then it was buying more waves of attack and counter-attack, but it'd be lots of fun if it was buying waves of tanks and aerospace, and it'd give something for units to spend their CB coffers on besides recruitment, but I'm getting off topic for this thread).
IS Omnis are another common request, as they're supposed to have shown up in-universe by now. (What ever did happen to "one-day-at-a-time"? That was honestly going to be the single most amazing thing about MWO, and the single thing that had me absolutely hyped when I heard about it, and it was abandoned before I ever got a new enough computer. That was likely the single worst decision ever made by PGI. It also would have accounted for balancing old weapons against new ones: you don't. "The timeline is progressing, and as it does, technology is improving, leaving older outdated equipment in the dust". We don't use F-4 Phantoms, anymore, even though they were amazing in their heyday).