Fixed powder scopes can work just fine.
Downsides, AO is almost always on the bell. A pain to work when prone.
There is no plan B if mirage gets too high.
Because there is very little demand, fixed high mag scopes have very few options especially with reticles. Sightron is now offering custom reticle swaps so that might not be that big a deal but once you add in that cost, you may as well have purchased a variable with more features.
As for the Savage FTR, you really need to get behind the rifle and see if the stock fits. This is likely the worst offering out of the Savage line up. The palma stock is so much more user friendly. Even the BVSS can work or modified to work better.
As for the accuracy potential? Once bedded, they have a solid reputation for shooting well. As well as a good quality rebarreled Savage, probably not on average but you also dont need the time lag involved with swapping out parts.
For the money, you can put together a rig that will offer better prone ergonomics and shoot more consistently if not outright more accurate.
If you are serious about putting a Savage together, I have parts so wait time is now nil.
Jerry