Here's a suggestion which doesn't quite fit your criteria, but which
might be near enough:

Decide which discipline suits you most - sounds like trials.

Now buy the best trials uni you can afford, because if trials is your
main thing, you won't want to compromise.

NOW you need an all purpose uni for a bit of freestyle, MUni, commuting
etc. But none of these is your main thing, so you can happily accept a
bit of compromise. right?

So get a reasonable quality 24 - something like a Nimbus 2 (Yuni 2).

Now fit a medium section tyre. Mine has a 1.95 slightly knobbly tyre.
It works for MUni but isn't too cumbersome for road use.

Now buy two sets of cranks: a long pair for MUni, and a short pair for
scooting about at high speed. Failing that, 110 or 125 mm would make a
good all purpose size. Choose 125s if you think you'll do more MUni;
choose 110s if you think you'll mainly be scooting around. Put some
reasonable pedals on - grippy, but less aggressive than pure MUni
pedals.

You will find that you get a sense of achievement from successfully
riding off road on a UNi which isn't really specialised for that
application, and an equal sense of achievement from riding fast or far
on a general purpose uni.

I've had a lot of fun on my basic 24, and have used the same frame,
wheel and tyre for all purposes, changing the cranks between all sizes
from 89mm to 150mm.


--
Mikefule - Roland Hope School of Unicycling

"Our greatest glory is not in never falling, but in rising every time we
fall."
Confucius
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