There aren't 12 shapes. My fingers say C maj, F maj and G maj are the same shape. D maj, E maj, A maj too. And A min is the same shape as C/F/G maj, but would be a different pattern on the proposed "regular" layout. That may not matter when all you want is transposition, but as I said before: transposing is not so important. And there are "shape" based keyboards, as mentioned frequently in the comments. You can even retrofit some on your own keyboard. They're just not popular.
C maj, F maj are the same, but C maj7 and Fmaj7 are not. Ultimately you have to remember which chords are the same and which aren't - which is about the same amount of information as just remembering all the combinations.
It's just an ugly irregular hack. I understand that you can get good at working around it, but eventually it's worth it to fix the underlying problem.
