Okay so after many hours I finally run out of ways how to do it wrong. The key was to use EXTERN() command and place both function pointers into section not marked as KEEP. From MPLAB® XC32 Assembler, Linker and Utilities User's Guide :

The EXTERN(symbol symbol ...) command forces symbol to be entered in the output file as an undefined symbol. Doing this may, for example, trigger linking of additional modules from standard libraries. Several symbols may be listed for each EXTERN, and EXTERN may appear multiple times. This command has the same effect as the -u command line option.

Pity alias do not work across translation units, overwise it would be perfect solution.