Bummer about the cut stock. For the scope mount, perhaps another of the type that had been mounted could be found and refitted to cover the 'ugly marks' and give you a mount that allows use of the wing safety? At least it doesn't have a dovetail cut through the receiver ring, as many 'prewar' MS do (or does it?).

If it's an unaltered Sequoia it's chambered in .30-'06, a major convenience with ammo being readily available and relatively inexpensive. As a 'shooter' that alone gives it great value.

If it were me, and the price is anywhere near reasonable (say, sub - $1,000.), and in the condition described, I'd likely jump at it, enjoy the heck out of shooting it, and scour every advertisement available looking for a buggered MS with a good stock. There's absolutely nothing like the action of a genuine, prewar Mannlicher Schönauer.

Reproduction stocks can be made, as well.

Here's one for an MC, perhaps he'd make a 'prewar' MS stock?
Cottage Craft Works