For the BS Zelda (remake), you can use the Mottzilla's hack, which combines both Third and Forth quests into one single ROM, and allows you to select your character.
As for Ancient Stone Tablets, sadly there is no way to play it in one single ROM at the moment :/
I had thrown into the air the idea of maybe remaking all of its assets into a ALttP hack (excluding the timed events for particular items), but there seems to be no interest in it.
I tried starting it, but couldn't get the hang og Hyrule Magic to change the starting point to the house near Dungeon 1.
The only technical details to achieve that would be the house, making a character selection and perhaps adding a random weather changer for the game, the rest could be rearranging ALttP's already existing assets to fit the AST layout and flags.