It would already be great if the flight plan loading of the present PLN format in MSFS would be fixed. No much use discussing new formats as long as this does not work.
Keep in mind that you can also create the plan in MSFS, save it as PLN and then load this into LNM for flight following.
Loading the plan directly through SimConnect is not as direct as one might think. You cannot simply transfer a plan through SimConnect to MSFS. The program has to save it as a PLN file first and then tell MSFS to load this. I suppose you will see the same issues.
Alex