This is the stuff DTK can do right now with notes on whether VScript can/should be able to do it:
Change a player's class - yes (I think)
Set their speed and move type (speed is a DTK thing because it's done using an attribute. This MI interacts with that. But if a VScript added the same attribute would that replace DTK's or add the same attrib again with a new value? Would it matter if it was calculated after the first? Can VScript do move type?)
Give them weapons, remove weapons, give a weapon attributes - yes, pretty much.
Set the player's health, max health and scale it up (if they're an activator) - yes of course.
Send a message to their text chat - I believe so.
Switch them to a specific weapon slot - not so sure about this. Involves sending a fake client command and targetting the weapon edict in the slot. I'd have to check.
Force them to be melee-only - this is a weapon switch and condition. It may be a good idea to retain certain 'deathrun settings' though if a VScript solution can do this it would be better, as all deathrun plugins support melee wielding.
Give them a custom model and make it use class animations - built in to TF2 now.
We can probably remove most of it with the possible exceptions of:
Move type
Switch to a weapon in a slot
'Environment' settings like melee-only, no medics, no healing, class limits, melee-only in a zone
This is the stuff DTK can do right now with notes on whether VScript can/should be able to do it:
We can probably remove most of it with the possible exceptions of: