I want to make the entire game into one continuous level with no breaks in between. Where one starts, the next one will begin exactly as it is in the vanilla game. Bowser levels will just involve getting past him and then the first stage of the next world will begin, with 8-4 being the only exception. There are some issues such as cycles though. I am not sure how these things are loaded into the game, do the cycles start as soon as the level loads, or is it based on your position on the screen like a lot of other NES games? I'm also concerned that every Bowser and bullet bill will simultaneously fire from the beginning rather than waiting until you get to the "beginning" of each stage.
I'm also not sure what the best way of putting this together is. I downloaded a Japanese editor called SMB Utility. I'm not quite sure how to use it properly yet, but it looks ok. I'm still not sure if what I want will be possible with this thing though.
Edit: Warp pipes will also have to be changed. This will be fine with things like the coin room in 1-1, but if the pipes warp to another level, the exit point will obviously need to be updated.
That does seem like the logical way of looking at it, and it's kind of true in some ways, but not in others. An example I can give is the use of save states in practice. It is obviously more beneficial to practice one stage over and over again rather than play through half the game just to have a crack at one stage. Doing it too much can actually become a problem though, both in a practical and mental sense.
You can forget the order of stages, forget positions of certain objects in stages you don't play a lot or just forget small things that save time. One example of this is in stage 4 of Contra, where if you start firing as the level fades in, you can get a stream of bullets going very quickly. It's easy to remember if you're practicing the level from a save state, but not if you're in the middle of a run and you haven't been playing through that stage transition often.
Sometimes I do no-reset runs of games without a recording or timer, so I can practice stuff like that in a setting where I don't start feeling any pressure if I'm on a good pace. This is one thing that would actually be partially removed from smb1 if this hack was made. Go and watch one of Darbian's smb1 runs and watch his heart rate monitor increase during the stage transitions and you'll see what I mean.