No, not the client sided player timescale.
I think it'd be cool to have a server sided time bubble event, like SetPlayerTimeScale. This way you can see other players moving in their time bubble while you're in your own. I think /timescale #Here should stop all TimeScale events and put everyone on the specified timescale though.
Mmm, also this would be fun for special rooms in DMs or RPGs, when you enter, you can either be in a slow motion timescale, or a fast time scale. Maybe this could go into the zones event mod? SetZoneTimeScale? I know theres zone events to simulate this, such as gravity and drag, but nothing does it quite like the actual timescale, because you have to take things such as projectiles into account.