By default the next note is half as long as the previous. But sometimes that's inconvenient. For example 9/8 is usually 3-3-2-2-2-2-2-2-2... A bar is devided into 3 dotted quarters and a dotted quarter into 3 8ths, and anything further down is split in half as is normal.

Oh that sounds great, but very difficult to read/play

Sometimes when there's a bunch of triplets the editor will just write "simile" and drop the triplet notation.

This could work like that and only the time signature would need a brand new notation, so no I don't think it would be super hard to read.

Triplets are tough to play haha