That's an interesting notion. I'd be interested to know if A) there is anything to confirm it, and B) if there is any indication to how many (if any) players come TO Battletech FROM MegaMek.
On the IRC network I call home, I've lured in players who'd never heard of battletech and taught them to play. I've introduced people I RP with IRL to BT via MegaMek too. Heck, I've even given megamek demos at a local Linux User Group. I would imagine it stands to reason that most people who purchase the products sold under the battletech label are players of one of battletech's flavors. Particularly the rulebooks, I have a difficult time imagining what use battletech rulebooks are to someone who does not at least intend or desire to play. With the plot sourcebooks, I suppose it is possible that there are people who purchase them to follow the storyline, but given that we're well into our sixth year of plot stagnation if that is their sole link to the franchise, and they have not given into despair then I must commend their willpower.
I think it is also likely that the more frequently you play, the more of the game you will have covered. I would have never touched most of the pre-generated scenario products from the FASA era if it wasn't for their inclusion in megamek, for example. Is it that difficult to believe that someone who spends a significant fraction of their free time playing Battletech, is likely to desire more material to feed their obsession, and will desire additional product? It certainly seems to me that the enthusiastic, frequent player is going to be more eager to purchase than the other extreme.
To what end, though? Say that we do end up with Clan ER Light PPCs and Heavy Pulse Lasers and Heavy ER Pulse Lasers and Ultra LB-X Autocannons and Rotary LRMs and Gauss Rifle Arrays and Streak Pulse Rifles and every other possible permutation of weapon prefix. What meaningful improvement does that actually ADD to the game other than slight shifting of numbers and dozens of pages to the next rulebook? Complexity is fine, when it is merited and results in an improvement to the game, but complexity for the sake of complexity is just going to drown the core concepts of the game with clutter.
Variety.
Customization is a big part of the game. I have a player right now who literally cannot touch a mech without trying to make at the very least some minor change to it. Seems to itch him uncontrollably to leave the mech stock. We have a whole forum for design. It's a major facet of what makes battletech battletech. And Eventually, you explore all the combinations of parts that are satisfying to you as a player. Sometimes you get ideas that you wish you could explore, but the extant equipment doesn't have room for.
Not every combination of prefixes is going to be meaningful, which narrows the scope of what prefixes are relevant to what devices. Pulse doesn't apply to a missile. Streak would be meaningless on an Autocannon. But I'd enjoy having a Streak Thunderbolt launcher. Heavy and Light work for both Gauss and PPC. It's also rather rare for double prefixes to be applied to something. We have LBX autocannons, and we have Rotary Autocannons, but we don't currently have Rotary LBX autocannons. Whether or not allowing them, would be a point of debate under this sort of expansion.
the nature of the weapons available greatly influences the way things play out post-customization as well. I play a mech with a Streak SRM rack differently than I play a similar mech with a Standard SRM Rack. a HAG looks on the surface, very similar to a LRM launcher, but the cases in which I would prefer one or the other varies dramatically. More equipment options means more play options.
To take an out-of-battletech example, Pokemon is a franchise atleast partially oriented towards a rather young audience (though it certainly has its grown adherents as well). As near as I can tell, there's currently 807 of them. Players do not have to memorize the type and movesets of each and every one of them, primarily they only need to know the far more manageable list of
types of pokemon, which only numbers 18 types. I haven't paid attention to the games since maybe their second or third generation, but I could hop right back in today and fight effectively against modern opponents simply by knowing the rock-paper-scissors relation of the types involved. I might not be the MOST effective player, but I wouldn't be entirely obsolete either. I'd argue the keyword abilities in Magic The Gathering are of a similar nature. I don't have to memorize that both the Force of Nature and the Lord of the Pit deal the remainder of their damage above a blocker's defense stat, I just have to know that "Trample" means that, and from then on, any creature I see with Trample, I know instantly what it does. I also know what Rampage does. and First Strike. And I could jump back into the game after not having played for half a decade, and rapidly learn what the new keyword abilities mean.
One man's "clutter" is precisely what draws someone to the game.
To take another example, I've been playing a lot of Bolt Action, a World War II tabletop wargame of late. But I find it deeply unsatisfying sometimes. All of the tank cannons are condensed into three different classes of weapon. What were in the real world very distinct weapons platforms all wind up feeling very generic. Flaws and failings get masked or buffed out, while advantages and unique character get washed out. The same thing happens at the infantry level. One SMG is more or less treated like another, despite some of them being very flawed weapons, and others being superb. It doesn't prevent me from playing, but it doesn't engage me on quite as deep a level as battletech does.