1) You know USA buildings have security system and rangers after destroyed, China buildings have mines. So ALL of the GLA buildings should have fortifications upgrade and reconstructions after destroyed. Currently, Stealth and Assault buidings don't have fortifications upgrade.
2) Currently, Stealth is very weak vs other generals especially USA and China. I think maybe his defence buildings are passively stealthed, not have to be upgraded like the original ZH. And maybe some of his vehicles are passively stealthed like quad cannon ,toxin tratcors and so on.