Irrational Time signatures
Irrational Time signatures (the bottom number is not a power of 2, for example 5/12 or 4/5 or 10/11) are not very often used in music, and for understandable reason as they are often difficult to read or write. However, it could be useful to sporadically add an irrational time signature in a mixed-meter piece such as the one linked below as a way to create faster notes without having to change the actual tempo every 2 measures, which could be more difficult to read:
Personally I think experimenting with time signatures such as these could prove interesting, and to solve the problem of "well how the hell do you define a 1/3 note," you could just divide a whole note into thirds using triplets
My suspicion is that any suggestion by Joe Average MuseScore user to enhance what the software can do in this regard, will be met with swift response along the line "MS doesn't provide this, probably won't, why not just use the existing vogue in meter creation?" I've created & used assorted constructed-meter time signatures, such as "4+3/8" or "2+3+1/4" - mostly to reflect how I desire the note-groupings to be 'felt'.
To an extent, I agree. The developers working on MS4 have loads more issues to address.