Tomas,
I think I found it.... instead of cl_bcs use CL_BCS_MESSAGE. This does not commit nothing until you call send method and you have choice if you want to do it in update task (method SET_UPDATE_TASK). During save method it checks if you want update task or not and then it calls FM SBCS_SEND or SBCS_SEND_UPDATE. Seems like now wrapper function is needed for that (as long you don't want to pimp this class).
Example of usage can be found in program RSBCS_EXAMPLE_EMAIL.