A solution to NOT drill your track forks and have a normal front brake nonetheless

Might be an idea to just make one and try it and put the theory into practice?

As each set of forks is going to be different at the bottom then it is not a concept that can be generally applied and each fork would need it's own dedicated design so making it to work with your fork and your fork only should be the aim maybe?

A single adjustable expander would work for most steerers.