UKF are already gimped by being unable to wire off until tech up, removing sandbags from them would render maps that have no cover especially on important areas an immediate veto for a faction that revolves around cover.
You want to solve this "issue", make it unable to have green cover created inside capture areas, instead being able to upgrade the capure area with defences for a cost, that way, you lose it, you give dences to the enemy.
One will simply have to test and see but the majority of map provide all type of covers. Point here is that IS currently should be balanced around fight in green cover and full health and that is part of the reason they are difficult to get in the right spot.
One can more the sandbags to Ro.E. and make any adjustments needed to IS.