I know this can be done without needing to change class at a CP, this unitpack has a unit that does just that:
http://www.gametoast.com/viewtopic.php?f=35&t=27134

The DL link is broken, so here's the version I have if people want to have a look:
http://www.mediafire.com/file/di4ht5f9y ... FICIAL.zip

I don't have access to that source code, so I don't know how to replicate this but I would like to know.

Before someone asks, I've read the sticky link on setproperty() and tried to get it working before posting.

The Gun Game Mode by Razac920 makes use of a function that instantly respawns the character in place with a new weapon when a condition is met. However, that user didn't publicly release the source files for that mod. I'd ask him for a copy of the source files, he may be busy so don't expect a quick reply. If you can get them, they could be used as a reference.