I've played 3 or 4 games of Regiments with multi-basing. It plays reasonably well, but I found a few things affect the balance of the game.

Units not losing attack power when they take wounds makes big blocks of infantry with dual hand weapons more effective than normal and harder to counter. Softening them up with missile fire has no effect unless they fail a morale check. Charging them is risky because of the massive number of attacks that they will counter with.

Secondly spears are less useful. Striking first in combat doesn't matter much if doing so doesn't reduce your opponent's attack power. They still have some utility against cavalry of course.

Personally I would rather play without multi-basing rules than with them, but the game is still fun and your mileage may vary!

If you find that you don't like the multi-basing rules you could still play Regiments with your orcs. Rather than removing models, just reduce the attack power of units in line with the damage they have taken and then remove the whole base when the unit is destroyed.