If it was my lake , and it is not, I would go ahead with the BG/forage pond you thought about and also add the adult LMB. Depending on the size you find I would stay on the low end by weight. Try for 300 lbs of 10-12in LMB appx 1lb each. It is not easy to find those adult fish from a known source. It is necessary that you know about the source . There are folks out there selling 4-5 yr old 12in LMB that are stunted. You don't want those in your lake.

Good luck and let us know what happens.