I like the idea of including some blank power-up templates. I wouldn't blast the Hello Engine as much if Hello did that.

I wouldn't add too many enemies, though, since there's little use in making this another Hello Engine. I'd probably have a Goomba, Spiny, and Red Koopa, though.

When you add these enemies, are they going to wait until the screen gets to them or will they always be active?

I'm going to include all enemies from SMB1 (including Bowser), and some blank templates for custom enemies.

EDIT: @ Miles lol we posted at the same time

Wait until the screen gets to them. That's better, IMO

Miles here with an all-new suggestion:

You might want to use different keys than Z and X, and then make notes about the controls (and this situation) in the game information screen. Many keyboards can't handle an arrow key + more than one of those letters pressed at once. Say you were to have to make a running jump - some keyboards won't notice all the keys pressed, and you'll run into a bottomless pit rather than jumping over it.

I'm guilty of using those keys myself, and when I had to use a different laptop when I was working on my Mario game on the road, I found out this terrible problem the hard way.

Whenever I make a game now, I always map the keys so both SHIFT and X operate the jump button, and likewise with Ctrl and C for running. Different people prefer different settings, so I give people a choice. Freedom and liberty for all!

Extra points if you add a way to customize the controls like you see in Djrellik's engine and some of the really polished fangames and indie games.

I'm planning to add an in-game control mapper. Default will stay Z and X, though.

Great!

Bad Dazzle bad. Bad, I say!

That is one of my favorite control schemes, but still - read my post above about it.

Lol. I'll look into that...

Are you going to add climbing?

Maybe, but I added the climbing sprite for the flagpole system for now.