It all depends to the market demand. That is really true.
Here are examples of ROV companies - Oceaneering (S'pore), Fugro (S'pore), TMT (Australia), Alam Maritime (Singapore) which is mostly seen on a construction barge is Malaysian Waters.
Diving Companies - Sarku (Malaysian), OWA(Japanese), Caldive (Not too sure)
Future investment I would suggest ROV. Pays a lot better than divers. (depends on the position). I work in the offshore construction industry, and what i see is more ROV friendly equipment been designed in the market. More clients are thinking of this future way forward not to use divers. But there are still works that divers are the only ones know how to do it.
Offshore Industry: Construction, drilling, subsea inspections, pipeline repair some examples where divers and ROV are used depends on the scope. Also, its divided into two, deepwater and shalow water (100m below). for the deepwater no divers are used. And for the next few years deepwater jobs are coming up in Australia, Malaysia, Brunei, and Indonesia. So i believe demand is there.
ROV license: Most of the Malaysian guys who are really expereince, they work outside malaysia. This is because in Malaysia, they cant get the market rate (which sometimes reach 1000pounds/day) depends on the position. And earlier days they go and invest their own money to take license in Aberdeen, Singapore, Australia (places which i know of you can take license). Its quite expensive but after 2 or three trips you can get your ROI (return of investment).
So in summary: I would suggest you to take ROV. But needs knowledge of hydraulic, mechanical and electronics as basic. Plus you dont get wet..