One thing that would be useful, would be expanding your mud search to include races and classes.

For example, I don't know if this is possible, but maybe the form for adding a mud to your database could include free-form boxes (one for races and one for classes) with instructions requesting that each race or class be placed on a separate line in the appropriate box.

Then, in the advanced search, you could provide three keyword boxes for race and three keyword boxes for class, with commentary saying something like "The mud <i>must</i> have the races listed below:" and so on. When the search is done, only muds that have these races and/or classes in their list of races and classes would be included in the output.

And if feasible, you could even go so far as to let muds include a list of their areas, along with the warning to the searchers that searching for specific areas may slow down their search considerably.