Custom Field Type - Have a crazy one for you.
A file type that can operate as both single or multiple selection. each option can be designated as being able to be one of multiple or single choice only.
(field name) Service:
Here is where the twist comes. In the case of winter work it would be more convenient to allow multiples in that same field.
Would be better than creating a separate service filed when only one can be used per deal and it would be better than spelling out multiple scenarios for that winter work. If there was a way to designate each selectable option as being able to be multiple entry or single entry only that would solve the problem.
Maybe groups of values that could be a part of multiple.
I haven't thought through about bulk editing and I have no idea if something like this can even be engineered.