I am going to get trash cans thrown at me from all directions now.
We were doing all you are doing here about four or five years ago, and finally came to the conclusion it really wasn't worth the bother.
Ok, you can most probably get a DRO 'setup' for just over a hundred bucks, but for how long.
We found that about 6 months was a good length of time before they started to go wrong and you were chasing your tail trying to repair them or get replacements. Normally, it was a lot sooner than that.
Of course, if you only use you mill only very occasionally, and you clean up every microscopic bit of swarf and dust from them and use no lubricants at all, them maybe you will have a system that will last for a fair while, but otherwise, expect all sorts of problems, especially when the damned things fail half way thru a critical machining operation, DAMHIK, but it happened many times.
When I set my 'cheapo' system up, I extolled it, just like yourselves. But time and experience soon showed me I had made a mistake, and after spending more than a top quality system to keep it going, I gave up and dug deep, changing over to that 'professional' system has really taught me, when it comes to cheap DRO's, unless you can keep them in a totally clean area (I use one on my quill) they are just not worth bothering with.
Save you pennies a little longer, and invest in the good stuff. Even a cheapo glass scale one will knock spots off what you are trying to do with these.