I think "ditch" is fine, but might "niche" be more in keeping with the sentiment (while preserving the rhyme for the many who pronounce it that way)?
The problem with "Dave" is that even people who don't read Latin or glance at the Latin will know immediately that it is a liberty taken by the translator, since there's no way Martial knew anyone named Dave. The effect, I think, is to undermine the reader's faith in the translation. If you can fit a name that doesn't immediately tip the reader off that you are taking liberties as a translator, it would be better. If you can't, then I think leaving it out is the more prudent course.