I hear ya , I used to work in a shop that made tubular A-arms for cars and the customer would be like can we just shorten it up a bit , or move the balljoint .I looked at doing a 29" Megatrail last year, and it really morphs into a different model. As the wheel gets bigger, you have to raise the axle to keep the BB height where you want it, and tire to seat tube clearance drops very quickly. Next thing you know, it's a whole new design with different machined parts, different tube fabrication fixtures, different weld fixtures, etc.
You can run a 29" front end on a Megatrail, which I've done and liked, or if less travel works, the Trail Pistol with a 140 fork is pretty capable. If you're riding somewhere that you're wishing for a DH bike, it will be short on travel, but for most rides, it's pretty awesome.
We always said yes BUT!!!! it would require , this , this and this being changed to start . end result was ahhh just leave it the way it is LOL .
As for the Megatrail it,s on the radar again . as it,s less travel than ,my 167 and it is lighter and fits a waterbottle in the frame LOL .