The larger the stakeholder the more aware they become. We can point to that when the hostile takeover happened. As soon as a sock puppet fitness penetrated the top ranks it was like a battle alarm went off and everyone woke the fuck up.
For the loan attack to work you would need 51% of all voting power to be lazy and stupid enough to rent it out to a malicious attacker. As soon as that attacker got into the top ranks the witnesses would have to still do nothing. That is highly unlikely as all it would take is a few stakeholders pulling their loans off the market. Combine that with Vitaliks idea of a time lock on gov changes and the attacker would be sitting there in board daylight with their pants undone.
This attack would be impossible on Hive as combining social and dpos makes for a really tough competition and such malarkey would be spotted early on and called out. Keep in mind your actions have consequences on stake based systems, if you're caught loaning your vote to an attacker that tries to take over the network you can get your funds forked out or frozen. Large stakeholders need to be aware of this.
RE: Moving beyond coin voting governance - My Thoughts