That’s a terrible idea. County sizes (both population and geographical) are functionally random, and a state could give themselves more votes by making more counties. Just look at this map to see how gamed the system would be from the start: http://www.freeusandworldmaps.com/html/US_Counties/US_Counties.html (especially compare AZ to NH or AR) and then picture what happens if states get rewarded for their county count. If you want to go apportionment go with the NH system of following the congressional map.
My proposal is tongue-in-cheek because Republicans would own the presidency in perpetuity the way the map is laid out now but it sounds “fair” to low-info voters.
I’d never expect the Dems to agree to it.
As to one vote per congressional district, the only problem is that the congressional districts themselves are drawn according to the census so all one has to do is rig the census.