One thing I could see us doing if we had enough people interested (and as far as I know, we don't) is setting up two leagues and then having them play a championship against each other. The catch here would be that the two leagues would have separate player pools, so there could be overlap between the two teams in the championship. That sort of thing is the only way I can see to accommodate an unspecified large number of interested Redscapers.
As for how much the player pool would be watered down by adding two teams, and thus 52 players (more like 55 if you account for DL spots)... go through the RBL FA pool and try to assemble two rosters' worth of teams. They will be all kinds of ugly. Here's the starting lineup for one such team (the "better" one), based on overall 2011 ratings:
C: Carlos Ruiz
1B: John Mayberry, Jr. (< 300 ABs) (would actually be Daniel Murphy but I'm putting him at 2B)
2B: Daniel Murphy (< 400 ABs)
3B: Alberto Callaspo (again would actually be Murphy)
SS: Marco Scutaro (< 400 ABs)
MI: Orlando Hudson (< 400 ABs)
CI: Scott Sizemore (< 400 ABs)
OF1: Gerardo Parra
OF2: Will Venable (< 400 ABs)
OF3: Allen Craig (200 ABs) (Mayberry would slot in here)
OF4: Jon Jay
UTIL: Travis Hafner (<400 ABs)
There's only 4 major league regulars in that lineup (and speaking as a Cardinals' fan, that's being generous to Jon Jay). That's not to say this is a lineup of nothing but scrubs. There are some players in there that have been, can, or will be valuable contributors. For example, I can pretty much guarantee Allen Craig would have been rostered had he not gotten hurt. But there's also Orlando Hudson
Anyway, the point is, for 2011, you'd have had all kinds of trouble scrounging together counting stats with that kind of playing time. There are some SB in there, but not one of these players hit 60 RBI or R (there were 6 FA, with generally abysmal rate stats, who managed to hit one or both of those marks).
And this is assuming that there are no "mistakes"- that the additional players picked are the absolute best of those available. I think we all know from personal experience that isn't how things go.
Of course, you wouldn't actually end up with any teams looking like that, but adding 50+ players of that caliber certainly will water things down a lot. That might be a good thing, depending on your preference, but I don't think it's deniable.
Actually, I'd love to compare this team to a "worst" of team that would represent the league's 14th marginal team, but I'm not sure how to pick the players. Just picking the worst rated players would get me far too many injured players, late callups, and the like. Even including someone like Adam Dunn, who had plenty of ABs, might not make sense- he probably still would have been rostered in a 12 team league, simply due to potential. But if I can think of a way to do it, it would be interesting to see how the 14th and 15th marginal teams compare.