Does anyone see a problem stocking larger fish right away?
Not at all, just as long as you understand that all the fish have to be stocked at an advanced size, and that price increases according to the size of the fish.
The only caveat is with stocking adult LMB. There are 2 things that can happen.
1) If the LMB are feed trained, and you are not feeding, they might not adapt to catching their own food as well as feed trained fish that are stocked as fingerlings.
2) If you stock adult LMB from another body of water that aren't feed trained, they might not figure out how to hunt efficiently in the new pond, resulting in a weight decrease. Bob Lusk documented that in a pond that he stocked years ago.