Given that he has an established client base would he qualify for a LAH licence? The licence fees / insurance / income tax aren't all that expensive, particularly spread over the number of fares a full-time or reasonably enthusiastic part-time driver may complete.
There's probably a strong case for expansion of the LAH plate issue scheme. Imagine what would happen if your local publican started charging Dublin prices for pints of porter, T1990. I blame Kathleen Doyle for creating a National Taximeter Area (or the lad before her, your man who had the premium rate phone line scam... if it was during his tenure). Notwithstanding the fact that I can't remember who to blame, give it back to the City/Town/County Councils, I say.