Actually each entity has this property.
CustomerEntity.FieldsCustomProperties
The key is the name of the field, which will return another string dictionary of properties and values for that field. In LLBL Explorer if you open the field list, click on a field you'll see a custom properties tab which u can then add to.
I'd still argue that a runtime solution is more favourable, cause otherwise ur stuck entering (and maintaining) all those custom properties. Also i dunno how easy it will be for you to access those dictionaries as part of the databinding thingymajig.
P.S. I didn't check any of this, it's 100% assumption