There have been no decent miners under 500W released since the Antminer S3 in summer 2014. I'm not including Technobit's Minion boards in these considerations for the well-documented reason that that offering was mostly a scam; in any case, it was also summer 2014.

There have been two consumer/non-rackmount miners released since the S3 came out that allowed downvolting - the Avalon4 (fall 2014) and SP20 (winter 2014).

Nobody said it wasn't possible to do this. What we said was, nobody's done it in a year and a half and it's about friggin' time somebody did because it's what a lot of us want. What I'm saying is, if you don't want to, sell chips to someone who does. You make money from the sale of chips; with the exception of providing technical information to a very few technically competent people there is no customer service required on your part. If those chips go into miners designed for a customer base you are not serving, direct competition is minimized and you make money off miners you didn't have to build, you don't have to support and that are going to people who wouldn't have been your customers anyway. It's probably worth thinking about at least.