Medical Doctor should be a time-locked role.

[Kotlol]

Hard-disagree that time-gating would fix the tryst issue, self-treatment is just too good for most things to be worth the risk and delay of involving someone else.

The RP server "solves" this problem via rules.

To solve on classic it would have to be a mechanical change, e.g. making self-treatment not as good somehow. This is a whole can of worms in terms of balance and game design.

Pretty much a better fix yea. Like if you don't have "medical training" healing is less effective... but again that is a can of worms. 
I can think of 3 ways of doing your way mordent:
1: Doctors/medical drone/borg heal 25-50% better then others when using menders/hyposprays?
2: People cannot fully heal themselves past 70% (Thus being slower), unless a doctor/medical drone/borg does it.
3: Doctors/medical drone/borgs heal players faster. (Faster mender applying and such)

And even those 3 options.. still will get people in classic will cry foul.

Just don't lock the cloner to doctors/security only, cause then medbay will be nuked every round on classic :/ Not like it already is...