I have a request from someone who wants me to modify a single character from one of my fonts for them, but is also wanting exclusivity to the modified design (exclusivity in this case meaning I couldn't publish or resell this modified version; I'm not sure yet if it excludes being able to perform similar modifications for any others who might request it in the future).
Typically, for modified fonts, I've just done non-exclusive. So the client is paying for the design labor required and whatever the standard license is to cover their needs. No exclusivity fees are added into the cost, and I am free to be able to perform similar modification requests for others. (The only thing exclusive is the unique font file and name created for that client.)
Wondering how others typically approach this? If the desire continues for exclusivity with this modification, then I would think the cost would have to multiply quite a bit?