Not a good idea.
It will be difficult to use properly - it needs a cEntity parameter, which is hard to get in Lua. Plugin writers must not keep a cEntity object in a variable because it could get destroyed in the meantime.
It'd be much better to make a cWorld::AttachEntity(int a_EntityID, int a_VehicleEntityID) so that you can use entity IDs for attaching.
It will be difficult to use properly - it needs a cEntity parameter, which is hard to get in Lua. Plugin writers must not keep a cEntity object in a variable because it could get destroyed in the meantime.
It'd be much better to make a cWorld::AttachEntity(int a_EntityID, int a_VehicleEntityID) so that you can use entity IDs for attaching.