freeRTOS & System separate from application

i would like to have a minimal system running with the RTOS. the system would field messages over uart and/or can. it would have the ability to write application code to flash. and then start the application, and all the pieces would run concurrently. i want the application to use features of freeRTOS and system. and also would like to compile teh application separately from the RTOS & system. questions: what would be a useful minimal interface set to the RTOS? maybe all the defs in task.h? what would be a good way to interface to the RTOS? i was thinking of using SWI. in the portmacro.h i am using it is already used: #define portYIELD() asm ( "SWI 0" ) but i don’t think it would be too hard to add a hook for swi >0