MSX 1 smoothscroller general purpose engine
Awesome 
Looks cool.
What is the maximum level size for this technique?
There is no single answer. The quick answer is "consider the low 32k gone for the scrollers bitmaps".
Then you are left with something like 24k.
By the way, is there a way to use the bytes the disk drives steal without wrecking the disk functionality for later loading?
Snipping 32k sounds harsh, but didn't Konami games run without lower 32k?
Note that my saying "lower 32k are gone" are just my idea of what it is worth to trade for removing the wobblescroller shame.
There is no fix size/limit, watch the odd numbers the convertor tool prints to the shell (press a key to see bitmap mass).
But the scroller needs 8 charsets prerotated in RAM, that is the deal.
A normal charset got 4k, so 8 times that make 32k.
In current demo everthing is loaded to lower 32k except RAM-nametable (the part directly related to level size),
and BASIC sits in between, so first step to get more RAM is to move BASIC out of the way.
I favour BASIC for loading because unchanged code would BLOAD from cassette on a real MSX with drives turned off?
Nowadays PCs no more got diskette drives :\
Next step, there is somewhere an article about Turrican Tile Compression.
I haven't checked the method but I think this is way to go.
You would decompress stuff to the 16bit RAM-nametable the engine works on.
Having said all that. The 8x memory consumption is only for horizontal scrolling.
A vertical-only scroller on the other hand needs only one bitmap.
Then using 32k your level can have a whopping 8 charsets, i.e. 8/3 times more graphics
than all 3 vram charsets fully loaded. Sidenote, check docs about turning off Xscroll variable in convertor tool, then it will compress better.
The only caveat is that never more than halve a charset can be onscreen simultaneously or doublebuffering is wrecked.
To be more precise, no more than halve a charset simultaneously in one of the 3 vdp charsets. 9918 mathemathics is complex 
Sidenote, checking tripple buffering is todo. Then only max a third charset per vdp charset simultaneously onscreen.
Anyways, this is crying for a softscroll Knightmare getting programmed
There are many scenarios on the same base idea, ranging from extreme work trying to do a 50Hz game including
horizontal bleed wrestles to other extremes like a level consisting of BOBs.
On the other hand, you can do a Knightmare out of the box.
You get smoothscrolling and more charset. In this case the engine practically is better than the VDP alone,
except for the max-halve-a-charset-onscreen limit.
