IMO you need a forage fish established, and soon, or those FHM stockings will break the bank! But don't fear, for Northern LMB fisheries it's actually recommended by some of our experts to stock predator fish FIRST, and panfish [BG/PS] SECOND. So, you are not in a bad spot here - and the upside is your BG/PS won't likely get on top of your LMB and overpopulate. Intentional or not, you're sitting in a good situation.

I see nothing wrong with starting PS
and BG. In a pond with established predators you have to consider stocking advanced fish for fear of immediate predation otherwise. Nothing a few hundred sexually mature 4-8" BG won't fix, then just pray for 2-3 spawns this Summer. I have zero practical experience with PS other than researching them here on the forum, so I can't advise you other than to suggest the same - stock as advanced fish as you can find. I would personally treat them like RES and go with a 4:1 or 3:1 ratio BG/PS. So, if you stock 1500 BG in your 2 AC pond, stock 400/500 PS.
No clue what size your LMB might be now, but they are the apex predator in your fishery, and their gape should serve as your guide for panfish stocking sizes. If LMB are 9" and under, you can probably get away with 4" BG. If they are all 12"+, might need to rethink that size.
I am not a LMB expert by any means, not even close - so others can come in and help guide you much better than I. But, take heart, I think you're sitting in a great spot right now.