I used that arrangement back in the 1980s myself, but when keyboards evolved, so did I. I remapped the movement keys to match the other movement keys (arrowkeys).
If you're going to go to the effort of customizing your vim to force yourself to learn a new keyboard arrangement, customize it so that the movement keys are ijkl instead of hjkl, so that both of your sets of arrowkeys are in the same, natural, modern, inverted-T arrangement. Then you don't have to deactivate those real arrowkeys, because there won't be any temptation to use them with the ijkl keys in the same arrangement and easier to reach.
"Oh, no!" people half my age will shriek. "Then what happens to the 'i' key? This would be impossible." Just use the now-unused key on the left ('h') for your insert-on-left. Reach left to insert on left. There, easy.
Funny how those who insist that YOU should relearn something as fundamental as the entire inverted-T arrowkey structure built into the hardware of every keyboard and used by almost all apps on all platforms including kids' game boxes find relearning a single, arbitrary 'i' key such an insurmountable obstacle to themselves.
But what if you have to use a copy of vim on a machine without your customized .vimrc? Sorry, but that's just an argument against ANY useful customization of vim. It's just not a problem, because the real arrowkeys on the keyboard are in the arrangement you're used to using on the ijkl keys. Just use the real arrowkeys temporarily or copy over your .vimrc. I've done it for years.
But what about other editors that have a vi mode? What about something like zsh with a vi mode? These things can be remapped to match your .vimrc unless they only offer a couple of keys, in which case they can be treated just like all apps with their own couple of local keyboard shortcuts.
Really, if the standard advice is, "You'll have one or two frustrating days, but after that your muscle memory will take care of remembering "hjkl" for you," then you can take your own advice and keep the inverted-T muscle memory you already have for the movement keys and reduce your task to learning a single 'h' key for insertion, and save the next generation from this nonsense.
If a 30-yr user of vi like me isn't stuck with the historical accidents of the past, why should new users have to be?