If you want to implement "stop strokes" in D&D:

Standard AoOs are at +10 to hit.

5' step AoOs are at normal to hit.

If an AoO hits you when you are trying an action, the action fails. So if you try a 5' step from 10' to 5' against a reach weapon, and are hit, you fail to move.

You can choose to ignore the AoO stop thrust effect, but this causes damage from the attack to be increased by x10.

Next, some weapons are "short" range. A character can consume 5' of movement and enter "short" range with one designated adjacent opponent. This provokes a +0 AoO. This does not change which 5' square either opponent occupies. "Short" range is canceled if either combatant moves more than 5' away from each other. Any combatant at "Short" range must spend an extra 5' of movement to begin movement.

At "Short" range, you are a -4 to hit with any weapon that is not rated "short" range.

At "Normal" range, "Short" range weapons are at -4 to hit.

Next, remove the "Withdraw" action. Disengaging from combat should be hard and very dangerous.

Expected use: Use AC-boosting tactics, close to "short" range with an opponent. Once you are at "short" range, your target is in serious trouble -- they have to spend 10' of movement to get out of "short" range, which provokes a +10 AoO, which sort of screws you. :)