perhaps bluetooth?
Most important is plug and play on any computer without user action like installing drivers, if it can be done with bluetooth, why not, but USB has every computer and bluetooth only some computers.
The most important function is security though
Bluetooth would decrease the security, because anyone with bluetooth could try to crack the wallet, while with USB one would need physically contact.
Also I think it would increase the energy comsumption and the price.
iwould never buy a hardware wallet because there are to many people who are not happy with it and they are also scammed some of them so i dont think it is verry useful to take a bitcoin wallet.....