I fear that you are overcomplicating this whole scenario, and taking it way to seriously. If you love the way your Dell KB-522 feels, switching to a mechanical keyboard won't do you much good. Mechanical Keyboards CAN only be so thin, and if they are, you usually have to make a compromise, like with the Cherry ML ones. Just stick to rubber domes, there are some very high quality ones with a small form factor out there, literally thousands of options to choose from. I would usually go for the older models, but that's personal preference. Get opinions on small form factor rubber domes and select a few models. You can also look around amazon and order a few, they tend to not cost a fortune, send the ones back you don't like, and stick with one or two. I begin to understand why you have given up on mechanical keyboards, and perhaps that was a wise decision.