I would also oppose the extension of ATC to small GA fields, and am not persuaded that FIS is all that useful unless there is something complicated about the ground layout or unusual stuff goes on in or near the ATZ (Duxford seems to me an example of a place where FIS works well).
I would worry about ATC making some pilots over dependent on being told what to do and less alert to their own safety and that of others. There are already some GA pilots (a sizeable minority?) who seem over reliant on ATC and on r/t generally. Not so long ago at Waltham (a place where, as has been observed before, the basic, correct a/g service and the generally adopted habit of looking out of the window produces a busy but safe environment with little radio chatter), I and other aircraft were gently troubled by an aircraft departing for Booker who wanted a clearance to blow his nose or stick his finger in his ear (he appeared to have his finger stuck somewhere else, having been cleared for that from birth).
This keen reader of CAP 413 eventually showed some initiative: he decided all by himself that it would be a good idea to line up and then sit motionless on the runway waiting for a take off clearance. Admittedly, he was a particularly ATC-dependent example of the species, all he did was cause minor inconvenience to a few others (in fact I sort of appreciated the go-around practice as I hadn't been flying much lately), and, once airborne, he may have been a hotshot stick and rudder honcho who could fly rings round me, but his antics did not inspire confidence in his airmanship, and would have been less amusing if someone had needed that runway in a hurry.
As I said, this was a particularly bad example of ATC dependence, but I would worry about this sort of thing spreading if more and more of us train and habitually fly only under ATC.