...allowing players to add tokens. This way they could add their own players and in case of an unexpected encounter it would speed up things if for example , one player searches for orcs , the next player adds a few trees etc. while I arrange and assign things.
You can already do it by giving the players the status of co-GM.
After some thinking about disabling drawing tools for players, I am not so sure anymore that it is useless.
Whilst it is your problem as GM to choose your players and be clear about what is acceptable or not during the game, it stands true only for your usual group with known players.
If I was to propose a game to complete strangers, I think I would like the possibility to disable drawings. It would prevent immature players to completely ruin a game before being kicked out. I don't play with strangers, so I don't feel over concerned about it, but I can see a use.