Personally, this seems great to me, now during a base siege the defenders can ninja repair the POB (if the attackers can't keep up the siege for the whole time, or get driven off).
The consumption rate numbers could be tweaked, I suppose if it ends up too much of a buff to the defenders, promoting more RM shipping and giving the siegers more time to destroy the repair / supply ships. Or simply as you said, reduce the effectiveness if the base shield is up, so attackers can keep up the pressure even with a single smaller ship.
