The up to a year wait is for parts from Gravel, you are free to order them yourself and then once they are all in your hands you can send them to him to build the conversion, once he has the parts the barrel build and fitting only takes a few days. Just give him some notice so he can order a barrel blank. The wait is for the backordered parts not for him to do the conversion.
He is in the process of getting his manufacturers license (may have it by now) and then he will be a business and will be a site sponsor but in the mean time the longer you sit on the fence thinking out loud the longer you will wait to get the rifle.
You're thinking out loud is why he won't order all the parts and the barrel for you without some commitment on your end. It seems that all you do is think out loud and he doesn't want to get stuck with a $1000 conversion when you change your mind down the road.
Of course it's expensive, you are asking for something that requires a lot of money in parts and labor.
I haven't heard of any conversions Herron has had to work on to get functioning, care to share some details. The only conversions out there to my knowledge are Herron arms 223 conversions, Dlask 223 barrels and some Questar barrels before they got out of the ACR due to lack of parts availability from Bushmaster. Other than those conversions the 300 Blackout I had built and the 3 or 4 1911 built are the only ones out there in Canada.