It's actually already possible to affect the master tempo but you won't get any feedback.
re #101 Fix target UI
→ <<cset 8223d99f67ce>>
re #101 Give bpm values more space
→ <<cset 69308ab30fd6>>
re #101 Add "Round target value" mode option if target supports it
Currently only tempo target supports that.
→ <<cset 2f752a65edc2>>