I don't agree that flat top guitars sound better "99% of the time" than an archtop guitar. I picked up a pre-WW2 archtop last year and it has a great sound - different from my Martin and Gibson, sure, but just as good in its way ... and it isn't even a celebrated brand. Probably made by Harmony though ... well, possibly.
My view on violins is they're fine as they are. Grover style tuners would make them neck-heavy and bad for balance - although I know some players of 'old time' like those kind of tuners and cope okay.
Fitting fiddle strings is easier than fitting mandolin strings (4 not 8), and less dangerous. Just make sure you have a pair of tweezers to pull the A string through to give enough length for purchase ... it can get cramped at that part of the peg-box. And you can always use a tailpiece with integrated tuners and make fine adjustments at that end if you need to.
Don't know about Swarb ... but 'Rags Reels and Airs' has a cover photo of such tuners on his fiddle... but I believe it was a hardanger fiddle in that shot. Might be wrong ... it was a long time ago.