Jay. I like your design but prefer a smaller valve. If you put a 3/8" half cuppler on the outside of the TC instead of the 1/2" nipple then I could get/attach one of these valves (Their dip tube not needed) and bam, Bobs you're uncle!
Try something like this:
https://www.google.com/imgres?imgurl=http%3A%2F%2Fwww.shop.bhombtubes.com%2Fimages%2FMini%2520ball%2520valve%2520MF.PNG.png&imgrefurl=http%3A%2F%2Fwww.shop.bhombtubes.com%2F1-4-Mini-Ball-Valve-Fitting-T316-Stainless-Steel-14MBVMxF.htm&docid=9fJI39wBPBVcOM&tbnid=ITVcd-i5gCEU2M%3A&w=268&h=268&bih=916&biw=1829&ved=0ahUKEwjpj5Tn3dDNAhUKySYKHSLaD94QMwiiASgbMBs&iact=mrc&uact=8
I have two of them and they work great...this is what I plan to attach to mine.