Hi MikeHotel and welcome..
I am in a very similar place, and im currently trying to decide which way to go about it..
As you know,doing the GA Instructor rating first means that you will have to knock your commercial stuff on the head(cost for you unknown to me??), and then get into your Ins/rating which could cost between 10 and 12 grand..It is relatively easy to transfer over to an RA rating from there(i think after a certain number of GA instructor hours-200 maybe-it may well just be the paperwork and your 25 hours in an ultralight,but my memory could be wrong on that), but as someone mentioned earlier , some GA pilots do take a little while to adjust to the stick and rudder sensitivity and reflexes required in planes that could well be less than half the weight of what they were flying before.The point is that it would be good for you to start getting a handle on tecnams,jabiru's gazzelles etc for your own experience if you want to go that way..
Doing it this way will take longer, and cost you a fair bit more money short term, but will give you much more flexibility moving forward with the different types of work available, and will make you ultimately more employable at the ever growing number of schools that teach in both RA and GA.
On the RA side of things...You can start to make a buck a bit earlier and with less initial outlay, but it wont be big bucks, and you will still have to keep going with your commercial subjects and do the GA rating later on.The RA rating will cost you about 6 grand..One of the upsides is that 750 hours of RA flying can count towards your GA hours, and it is a good way to buff up the logbook, but as you already have plenty, that may not be something you want or need.
I guess it comes down to what your ultimate goal is.If you want to go on to fly charter/airline/other commercial work, then i would probably suggest the GA route and get the crossover going, but if you want to instruct at your local airport and go home every night and arent in a hurry, then RA may be a go for a while anyway..
Long winded, but hopefully some use..
Cheers
Simon