In an airworthy certified airplane, the electric stater cannot be engaged with the master off. If it can, something is really wrong!
Yes, leaving the master off during hand propping would prevent unintended actuation of starter - but a cautious pilot should prevent unintended actuation of anything!
Many smaller Continental power planes up to the late '60's had a pull starter knob, which was independent of any other control. They required a hearty pull to engage the starter. They worked extremely well, other than for two big dislikes: If they were set up incorrectly, they could really damage gears in the engine (the starter was turning gears as they engaged, rather than after engagement), and, instructors did not like the system, as it was a difficult reach across the student, with an awkward pull to start from the right side. Reaching across to turn the key was easier.