Needed-Better than plastic heater control valve-chronic problem

[Louisiana]

Hey folks,
I haven't found where this has been addressed so forgive me if this is passé.
Concerning a '99 GMC Suburban;
I need to find a substitute control valve from another application or make up a valve using whatever fittings are needed to get rid of this plastic. I know someone has already invented this wheel but if necessary I will keep working until I eliminate this fragile piece that has already cost me (and many others) well over a thousand dollars in parts and break-down-beside-the-road-costs and probably more than that in lost income.
My story in brief; When one or more of the ports break off at this valve the coolant is instantly pumped out and Vortec heads very easily crack. (I proudly own four cracked heads now) I recently replaced the heads because of this and replaced the crummy plastic Y and T connections (one of them broke at the same time as the control valve) with all brass fittings. While at it I put a small shut-off valve in each hose from the engine so that I could shut off the coolant from all the heater components if anything leaked again. That is as long as it didn't break so suddenly that the engine was damaged again. I could not find a metal control valve with this arrangement however and bought a new plastic replacement valve with the idea that I would replace it like once a year before the plastic had time to degrade. Good intentions, right? This was about a month ago. I was about five miles from home a couple days ago having just looked as usual at the temperature gauge when I looked again and it was pegged over on hot. I instantly pulled over and turned the engine off to find the new heater control valve broken. It was still supported as I had arranged it on the inner fender panel and the port for the hose with incoming coolant was off with the broken nipple in the end. My engine does not run too hot at all so that is not the problem. I just drove it on a seven hundred mile trip up mountains without a glitch after putting the engine back together.
I watch my gauges a lot but this happens unbelievably fast because it is never a leak. It is a dump of coolant without a clue when it happens on the highway. I planned to put a warning light to augment the gauge and controlled by a heat sensor in the opposite head from the one on the driver's side.
Look guys, I am a drag racer, former motorcycle mechanic and retired now from GM. I build my own engines and have since I was a kid. I have a business centered around muscle car parts. I am not doing anything too stupid here, I don't think. This is a piece that has cost me and a lot of other people a lot of money and grief.
What I want to do is simply put manual valves there to switch when needed and I may do that, but my wife wants it to work automatically and the weather does change a lot here in Northeast Louisiana.
If I come up with a solution such as a substitute, I will post it here. Meanwhile, how have others circumvented this flimsy arrangement?
Thanks for reading my rant guys. Now I can't wait to hear what others have to say.