Postal addressing doesn't map onto geographic coordinates anyway - sometimes, you can have multiple addresses sharing a set of coordinates (eg, apartments in a tower block) while at other times, a single postal address can cover a very large geographic area (eg, a university campus). Traditional postal addressing systems have pretty much cracked that for established populated areas, with the use of street addresses, postcodes and zip codes, etc. The big value for location encoding is in places that don't have a postal address - up a mountain, in the middle of moorland, on a clifftop, out at sea, on a rural highway, etc.

As far as the Maidenhead system is concerned, it follows a rigid format of letter/digit pairs - for example, AB01CD23 - so you don't have the problem of potentially mistaking numbers for digits. It doesn't have the l/1 or 0/O issue, because they can never be in the same place. If I was reading one out over a phone (or a radio, which is what it was originally designed for), I'd use the phonetic alphabet for the letters, but that's not essential.