I'm not sure about chosing initial angle and direction of the kuski. The direction doesn't really affect anything but angle... Figuring out how to volt/gas/brake at start to get to the right position is one of the challenges of many levs, that would be ruined :/
As Lousku said, nothing would get ruined. Old levels are not affected. You can still make levs where the initial position is classic (facing left).
Trigger apples, moving polygons, event scripting etc are abandoned ideas?
Pretty much yea. Hard to implement.
the power to change all the initial bike related variables, even velocity vector.
Besides initial direction, angle and velocity, I can't think of any other variables that would be useful to modify. Maybe angular velocity (rotation speed)? Would that be too much?
One-life battles wouldn't be a problem because there could be an arrow indicating the initial velocity.
how about a description field that could be made as long as needed?
Yea, it's a good idea.
Currently the sky background scrolls left and right while playing. There should be an option to make the scrolling: Left/Right, Up/Down, or Fixed.
I think it would be enough to have two options: moving or fixed. I think vertical-only or horizontal-only scrolling is not necessary. Original Elma doesn't have vertical scrolling, which is why you can't notice if you're falling down (for example). Everyone's used to it, but it doesn't really make sense.
It would be cool to have the option to put ANY picture into the level. Like anything dl-ed from the internet. But maybe it would increase the size of the levels too much, so I am not 100% sure about this idea.
Yeah I'm not sure about that idea either. I think it's better to have the graphics stored in one place (LGR).
The ability to rotate and (maybe) resize pictures, and the ability to crop pictures (in case, for example, you want to use one branch of a tree and not the whole thing).
Rotating and resizing pictures is definitely a good idea. Cropping - why not, although I can't think of any other use cases...
more top scores hh.mm:ss.xxx maybe with date of the record
Scores won't be saved in level file anymore, but in separate files.
All the other suggestions were related to level editor (or battles/bugs), not the level format itself :) but of course the level editor will be as good as possible.