TGU
Do it all the time in "area". Incoming phone call taken by Assistant, clearance issued by controller, passed by assistant on phone...probably to assistant on other end. Never had a problem with competence.
Similarly, clearances are issued to FIR FISO, who will transmit to A/C on their Freq. If you treat staff with respect and give them the necessary training and qualification we may be able to consign the us-and-them officers-and-men culture to the dustbin of out-of-date practices.
In your case standard clearances such as SIDs could be passed, it would still remain the controller's task to check the strip......but R/T workload may benefit greatly.
Good Luck.