How about a qualified yellow alert?
To me it's hard to say without knowing the quality of this divers training and how well he took to diving first of all. Going straight to drysuit is no problem. My concern is with thew "b word", boat. Common advice is to make the first few dry dives in shallow water where the consequences of an incident are minimized. Not too many folks hire on to a charter to dive cold shallow water.
It also being a first boat dive is not a huge consern however if surface conditions are less than prime being a new diver, getting out of the water in a drysuit and dealing with seas seems like an invitation to a trial by fire.
It equally seems like too many folks are too stuck doing things from a boat. I prefer incremental steps.
Other's prior experience is just that, totally scenario dependent, YMMV.
If the individual is a solid newbie with a good instructor and conditions are OK then it's probably not a big deal. Too many if's for me to say.
Pete