Personally, I have not had the problems with my gearbpx the OP did. If I just wanted an engine to push me along and function was all that mattered to me, I might consider friction. There are many plusses.
However, as I wanted to build an early motorcycle inspired bike and function, while very important, was not my only factor- aesthetics matter too....I'd still stick with my Honda/Grubee Skyhawk....or maybe consider an EZM without the cover.