Joel....look at the power pole closest to this building, and see if it has transformers on it. If it has 2 transformers, there is a strong possibility that the power company can give you 200 amp single phase service by just running a new service line to the building. If it has high voltage lines and no transformers, the power company probably took them down and just left the pole and lines to hold the right of way. They can easily hang a new pot and run a service. If they can't. second 70 and I can! You can get your electrician to install a 200 amp meter base and 200 amp breaker panel inside if the inside single phase panel doesn't already exist. If you have a Fluke meter, you can tie the ends of the circuits together in the breaker panel, and go to each fixture and ring them out. You can set the Fluke meter to audible tone ohm setting, and not have to look at the meter to know if they ring out. I see your point of not wanting to spend a lot of money for 3 phase service you will never use in an office/storage space. Let the next owner do that after the aforementioned bulldozer is done....lol.