Including PHP in options is not going to happen. Enabling something like that would require using the eval() function which is a security nightmare.
For what you are trying to do, the existing %type% breadcrumb template tag could get you part of the way there. It will output the types that the current breadcrumb falls under in a format suitable for placing within a CSS class. However, it looks like you really need a new %slug% tag. This won't make the 4.3 release as that's already done (just need to do final checks and release). Though I could implement it quite quickly (I think) and get it up into the GitHub repository shortly after the 4.3 release.