Should L and R modifier keys have existed, why not thumbs on bottom row?

I finished all of typing club months ago and learned to press left and right shift while typing letters on the opposite sides, but it became very slow and inconvenient to type shifted characters consecutively when on opposite sides of the keyboard, like "?!". Then I realized that I should just have one set on the bottom row and press them with my thumbs. On my MacBook keyboard I have OPT and CMD on the left side, and I remapped Right CMD and OPT to Shift and CTRL respectively. While it did feel awkward for my thumbs at first, it didn't take long to get used to it and my typing has been more efficient. Its not hard to press multiple CMD and OPT or Shift and CTRL simultaneously.

The benefit of using my thumb for the shift key on the bottom right is that I don't have to keep alternating between left and right shift, I can just hold it down with my thumb when typing consecutive characters, and can keep it held down instead of using caps lock when typing in all caps. Since I started using Vim I mapped the caps lock key to ESC since its used frequently. I don't need caps lock at all anymore! BTW, I stopped using arrow keys entirely and mapped them to CTRL H J K L respectively since that's what Vim uses alongside arrow keys.