I discussed this same idea already with several ppl nostr:npub1arkn0xxxll4llgy9qxkrncn3vc4l69s0dz8ef3zadykcwe7ax3dqrrh43w nostr:npub1gwa27rpgum8mr9d30msg8cv7kwj2lhav2nvmdwh3wqnsa5vnudxqlta2sz (nostride.cc) and nostr:npub180cvv07tjdrrgpa0j7j7tmnyl2yr6yr7l8j4s3evf6u64th6gkwsyjh6w6 (about if it would make sense to fit the GPX spec into a NIP / event kind)

I use Strava a lot (for my activities) and also Komoot (for building cycling and gravel routes).
So if anyone is going to build this, I would like to be involved 😉