Two big things get in the way of simply combining the AST ROMs into one:
1) Sheer size
2) The episodic structure pretty much enforces each episode to be standalone, which would null any point of combining the ROMs. You can't simply go from Level 2 to Level 3 or from 4 or 5 or from 6 to 7, which is what people would -actually- want from the combined set, even if it's not explicitly voiced out.
I would argue that it'd be easier to hack LttP and simply re-interpret the gameplay so that the game clock and episodic structure are non-factors, and the plot rewritten just enough so that there's no enforced breaks or waits.
That's the way I see it.
I read that combining all the four ROM's is nothing but a freaking pain to accomplish due to how different they are and how they handle everything.
Creating a ALttP hack that tries to keep it faithful to AST seems to be the only way to go so that we can accomplish a one ROM only game, although I think the only major issue would be making events/cutscenes for the new hack.
Hogwash. That's 8 stone tablets for 8 TOTAL dungeons, compared to LttP's 12. Just edit both the crystals and pendants into tablets. There's no other end-of-dungeon items to get in AST.
Hyrule Magic could surely handle that.
We can create all the 8 dungeons and make them all appear in the Light Overworld by getting rid of the Dark World, since IIRC the Dark World is not used in AST.
The dungeons could fit, no problem there, and the rent of the items could be handled by buying them instead of renting them, in a similar fashion to that of ALBW when you can get the full versions of them.
A lot of timed events could be handled by:
Once you accomplish something -> Enable flag which makes X appear
Only difference here would be that the event WON'T go away once you enable it, unless you complete it, which will unset the flag.
In theory, it should be feasible, but quite a time taker.