Very interesting “problem”. Locking to an IP address wouldn’t in itself stop someone from selling the account/vault. The “head” of my vault or routing can sit on any droplet and route back through to my local network (VPN/Ha). One could sell the hardware server access if all on same box. Locking may affect less technically adept home users, but if selling is profitable it will happen and IP address doesn’t raise the bar very high. Locking to hardware is interesting but its possible to “front” certain hardware so one could still “sell” if that is part of potential future plans.
The largest impediment is the bandwidth presently available to IP addresses you could have from Amazon, DO, Vultr if one fronted an IP address and ALL data had to travel over that tunnel to the Safenetwork. Some I wont name offer 20-50TB of bandwidth for relatively cheap so not impossible.
Maybe the second/3rd factor logins again has a place, especially if one can use a face and fingerprint along with privatekey for certain levels of vault aging. Nobody would buy an account where they have to leave some kind of master access to the seller. Removing that second/third co-factor or altering would reduce the ageing or reset it.
Anyway, something that creates an intense trust risk for a buyer for a period that is very uncomfortable would more likely discourage such a market than hardware tricks that can be overcome and inconvenience the average user (dynamic ip).
To be a little more clear, If I can make a Keychain for various powers on my vault but those “powers/users” are not in any way view-able until/unless used (Schnorr) no one would ever be able to trust buying a vault, ever. I could literally sell a vault with a “lower” or revocable “master key” and take back the vault using another key sometime after the transaction.
Excuse my tired rambling, but I found this interesting.