I was bored so I beat both Blazing Sword and Sacred Stones with only the Lord characters.
For Blazing Sword, I did the full Lyn Hard Mode -> Hector Hard Mode. The 3 Lords were allowed to perform and action and use any items I cam across. Other more generic units were allowed to give their items to the Merchant / Sell / Visit Towns but they cannot attack or rescue. They could also move around and die πSince I had no way to store items, I did allow the Merchant to pitch his tent so I could stock up, otherwise the challenge would probably be impossible.
The challenge overall itself wasn't too bad, but there were some maps which were just brutal, such as Cog of Destiny, I must've replayed that map off camera like 20x. Even the Final chapter came down to a bit of luck, as I almost ran out of Elixirs by then!
Very similar rules I set for myself in Sacred Stones, and I killed off all the extra units at the tower. I decided to go the Ephraim path because Erika has one boss which is nearly impossible for her to beat in her unpromoted form, a Swordmaster inside the desert castle. In fact, I had to start all over AFTER I realized this, but I remembered all my strategies when I played through again. Unpromoted, the chapter where the two Lords want to recapture their own home was probably the most difficult. In the end I spent all my precious stat boosting items on Ephraim, and a Boots item that gave him +2 movement which I got by pure luck in the desert chapter. The final boss is very easy in this game, and his attack only has about a 50% chance to hit the Lords, and I got quite lucky π