Yes, the old school FS bikes aren't quite what today's bikes are. But having 'updated' my '04 Epic (being more 'XC' , less 'trail' than the stumpy) has proved to be a great way to 'updating' the most important component... me. These last few months have proved a sharp curve for improvement, but things are getting better on every ride!
Don't think a 'modern' bike would be helping that curve. The old school 'steep' front geometry and slack seat, 26r, and narrow bars really accentuated errors. Actually a good thing, cause I'm more attentive to developing good technique. And it's working.
Now that I have a newer 29r, and after a bunch of varied rides, I'm not sure I wanna stay 29. I'm missing the quicker steering of the 27.5 (mullet of the epic... 27.5/26 ). I'm never gonna ride at speeds where a 29r really excels... so I'm hoping to try a modern 27.5 and see how it matches up...
Anyway, the 'update' of the old school FS has proved to be a great thing... I think an '04 stumpy FS might be even a bit more fun ! (with a 27.5 front...). If the OP's stumpy has the same Fox Fork as I have on my Epic, it'll take a 27.5 no problem, in fact seems to work better with the 27.5 , has plenty of clearance.
To the OP, as for drivetrain and shifters - I have had 3 weeks of riding on a Microshift 2x10 roadie, and the shifters were solid, consistent, really sturdy. Don't know about their flatbar shifters, but if anything like their roadie stuff, it's as good as 105 road shifters, for sure...
I wouldn;t hesitate to use for a 2x setup on mtb.
I haven't made any drivetrain changes, since the stuff is in good shape, running well. It's 3x, but I almost never use the outer ring, so it's mostly a 'ring guard' for the middle... LOL!
I'm good with the 'virtual' 2x, cause there's a clear difference in terrain I would use either ring on.
Personally the biggest difference, in order of magnitude, came from the 27.5 front, then dropper post, and then 720 bars (have 780 on the 29r, and it's WAY too wide for me...).
I might try 740/750 width to see how that feels...
OP ... all of this never happened - Unless you have PICS ! LOL! Let's see the 'untamed' Beast, now !!! LOL! (and then the 'after')
Ride On
Yuri