Reinventing the CraftA project that aims to add more functionality to Warcraft III, while at the same time keeping it a low size, so it's still useful for mappers. RtC will be available for any type of map, mod or even a Total Conversion.
1. Yes.
2. That really depends on how the map is triggered. If you want this cinematic playing for all players (which is probably a bad idea overall in case of warsoc) then I guess you can set some boolean variable to true when it starts and, before actually letting the player join, check if it's false. If not then you can display some "please wait" message, rechecking for that boolean regularly.
You could make a cinematic in "scenes" and have it do a check depending on when the player joins, display "please wait" and being it for him in the next "scene."