Question:
Would it be possible to have a logo associated to a meter account and to then use that logo on the billing?

Answer:
It essentially takes the top of your screen when you do the export or when you display the bill. So, as long as you have different organizations (with different banners); it will print with whatever is on the top of your screen, even if it is the same meter account visible to different organizations: it will print the banner of whatever account is logged in.
You can have multiple organizations belonging to one parent organization, with logins under roles under those organizations, with access 'restricted' to those entity meter accounts and/or tariffs. This means you can zoom in to one of those logins and still view the same meter accounts and tariffs. So you can have multiple domains without having to have different tariffs. It can be the same tariff entities, visible from different organizations?