Accepted that class G airspace isn't exclusive, however I still believe it would have been prudent to avoid that area.
I accept that operating an FJ at 300kts in relatively congested airspace creates it's own problems, I agree with your last statement entirely, there is a clear risk and I see no easy way of mitigating that without impacting GA.
I would say that Class G airspace is a lottery with no winners, it's ridiculous that I could be thermalling, potentially in cloud with no transponder and sharing the same airspace with a FJ doing 500ft a second. I was constantly on the radio on Mynd frequency advising my (approx.) location and height so that other gliders know it's a stuffed cloud and I always believed that was sufficient, I was reassured listening to other gliders advising that they were in the same thermal albeit at a different height, if I got uncomfortable I advised that I was taking a constant heading at x altitude, got visual again and looked for another opportunity, it wasn't worth the risk.
That doesn't work with FJ's, it isn't worth the risk because as you say it will happen because the odds are lowering as sport aviation is on the increase.