A WR250, 400, 425, 450 fork is quite an very easy swap, they are all the same.
And you can find them at very reasonable price.

Same goes for a WP fork. That is very doable as well, but a bit more work. Also to be found at really nice prices.

You really don't need OTR with their astronomical prices for another front-end.

New inner springs will also give you an improvement, but with a good sports suspension, front and rear, you won't recognise your Tenere anymore. Just depends what your wishes are.