What I think you need to look into are "trusts". There are many benefits to these for retirement planning, estate planning, etc., as well as potential for your situation of getting stuck overseas. You can specify who has access to the trust, under what conditions, etc. Pretty much everything we own is in our family trust.

The reason I am thinking about trusts is that your representative wouldn't have to go through the trouble to gain access to your individually owned homes, cars, bank accounts, investments, etc. These are all "owned" by the trust. And if your representative is a trustee, then they have access to it all. Of course you can set the trust up to limit a trustees access, but if you really wanted to give them the whole kaboodle, you could. You set this all up when you create the trust. And you can change the setup later, as your circumstances change.