I went with the Mamiya 645 Pro years back because as stated way earlier, availability of all options are still there and price point is good and only getting better. As for TTL in the Pro II, haven't missed it yet as all the old potato masher monster flashes work perfectly for it.....and there is nothing like showing up somewhere with your 645 armed with a potato masher, most folks have never seen one these days!
My only fuss with the 645 is that since it is manual focus, you really have to be on your game if you desire to follow kids around playing. Normally I hit 50% when doing so.......I have had to resort to my aging F4 or wonderful F5 to chase kids around with film.
I think you will find that none of us have never been unhappy with any medium format choice we have made. The quality improvement is so substantial that it's worth the hassle every time. And when you get everything right and the result is a spectacular photograph......then you know why you put up with the hassle. That, and honestly, it will take many, many more years and hundreds of photos to truly say "I have reached the limits that this camera can produce, I need something better." 35mm brought me into photography when I was young, medium format challanges me to be the best photographer I am. Have fun with yours.