Haha, that sounds so familiar. The shops around here finally make the switch, although one team mate still opted for a rim brake bike in 2020.
Yup, also that sounds extremely familiar 
My next bike will be 1x, I really don’t like shifting in the front. In case speed isn’t your primary concern, then 50:11 is way too tall a gear. Even with 40:11 you will still do 43 km/h at 90 rpm and 48 km/h at 100 rpm, which is plenty quick IMHO.
On a 2x the gearing you suggested is probably the way to go. Although a 1x conversion isn’t that expensive, you need a Wolftooth extender and replace the double chainring. Once you sell the unused chainrings, I don’t think it’ll be that expensive. Slap on an SLX cassette in the back and you are done.
But overall, if you want a cheap build, though, then the Merlin might be an option. It might be cheap enough to buy it and simply try it. You can always sell it later on if you don’t like it — and/or you upgrade to something else.