if someone doesn't enjoy new mechs and trying out new combinations then its unlikely they would ever play MWO long enough to care about the initial mechbay limit. If they are enjoying MWO that the limit becomes a concern then its highly unlikely they are going to be unwilling to fork out the small amount for a mechbay (at what amounts to around $1.50 a mechbay). Essentially a $30 MC purchase will give you enough content to keep a typical player going for 3-6 months easily. Mechbays are the only real part of the game that cannot be earned via cbills or grinding, and the grinding time is far less than other games.

mechwarrior is a niche franchise that appeals to an older audience and there wouldn't be many people who try out this game who are completely unwilling to spend anything.. Your typical console or PC non-pirating gamer, teenage or otherwise, is typically forking out $10-100 a month on games and usually these games are only played for a few weeks before they are finished and the player moves on the next product. With MWO you have access to months worth of content for just a fraction of that investment. The players who aren't sticking around are likely not doing so because of mechbays, but just because this game isn't easy and its not fun to get totally pounded on by more experienced players. The learning curve is steep and their is not nearly enough guidance given to new players to help them develop. Even so a lot of these players wouldn't stick around anyway, most are only after some quick button mashing fun and a high skill reward style game like MWO just isn't going to offer that.

Overall its the F2P model PGI uses isn't great but its hardly what is hindering the game. Its the new player experience combined with more work needed to flesh out game modes/CW that is required to create a more positive gaming experience. That being said the game is still going strong after 3 years which attests to some of the game being right.