tom, you've built a great game here.
I know its frustrating to see less players and less activity over time, but this is part of every game's life cycle.
considering the extremely niche nature of what you've built, the fact that there's no advertisement, and that the game is about ten years old now, the fact that its still going and still engaging to so many people is a testament to the quality and originality of the product, as well as your dedication and that of your volunteers.
take a lesson from other online games of the past, games which were way more mainstream with way more money behind them. almost all of them face a shrinking player base over time. what they do about it is what determines if they survive or not.
radical changes never work out. it doesn't bring in new players, it doesn't bring back old players (long term anyway) and it alienates the players you already have.
sticking with the program, as boring as that sounds, is usually the best way to go when you have a product that actually works. which bm absolutely does. you might add in a few features here and there to keep things fresh, take wow for example, but the overall product remains the same. and bm even has the advantage of being almost 100% player made content anyway, so your efforts in that regard can be relatively minimal.
I discovered bm 7 years ago, thought it was brilliant. played it for a while, then my lifestyle changed and I had no time for games period. about a year ago I found myself in a much slower pace of life and picked it back up. yes a lot has changed, there are much fewer active players, etc. (I came back right after the glacier/dwilight monster thing) but the game is still brilliant and engaging and I have a lot of fun with it.
mnf, though I'm sure its brilliant as well, has never appealed to me even from a cursory examination of the features and reading player experiences on forums. its not bm, and bm is the only text based game that has ever appealed to me, so its not surprising. and I was really interested to see what you had cooked up, I did a lot of reading about it.
ill close with this. one of the great curses of genius and talent is that so often the rest of the world just isn't on the same wavelength. think about how many geniuses and talented people went crazy because their efforts went unrecognized. think about how many of them self sabotaged and self destructed in the quest to get recognition for their work. now consider the pretty unlikely success of this game, to whatever degree. its something to be thankful for.
when davinci painted the mona lisa he probably didn't think much of it. some chick with a rich husband got a portrait done, some florins or whatever in his pocket, on to the next. yet hundreds of years later its his best known work and has captured the imagination of millions.I highly doubt he ever believed that painting would be the cornerstone of his legacy or even wanted it to be. but that's how it went.
its always the same for any creative endeavor. you put your idea out into the world with no guarantees, and people either like it or they don't. but when you go back and try to force people to like it by changing it to an extent that the original vision is gone, it loses its soul and its audience entirely.