As we talked about in the other thread, that’s not workable, and shouldn’t even be an option: all Julia packages (at least all registered ones) must have a main LICENSE file, independent of what is set up via REUSE. The template should ensure that the REUSE information for the .jl files in src and test match that main LICENSE.
In particular, you can probably probably have MIT as the main LICENSE together with MIT OR Apache-2.0 in REUSE, but you cannot have a registered Julia package that is only licensed under GPL-3.0-or-later WITH Classpath-exception-2.0. That’s assuming that this modified license cannot be put in the main LICENSE file and be recognized as “OSI approved”.