SymbOS MSX multitasking operating system - help needed!

Ah, ok, so the sprites will also stay with a ratio of 1:1? Meaning, that a pixel pixel is like 2 screen pixels?
Hope that it will be ok for a mouse pointer in mode 6.

Hm, I couldn't stop. Logical Copy made it to about 2500 4x8 blocks (this is the average size of a char in SymbOS) in one second (I hope I didn't make a mistake). This is about 1,7 times faster than on the CPC! I hope the final routine won't be much slower, but as the Z80 and the VDP can work parallel I don't see a big problem here.

A fast copy of 8x8 consume about 702 z80 cycles, so you can do a lot of things while you are waiting vdp command ending. Unique problem for real pararell process is non end of command feature in v9938. I was thinking in this trouble long time ago, and unique solution allowing this can be using line interrupt to generate interrupts to measure time waste in the 8x8 copy. I know that is a nasty solution, but this workaround could save a lot of time and free z80 to realize other tasks.

You can't do it for a running program directly, but you can start a new loader after you changed the address from autoxec.bas. (or the same loader if you do the move/run inside an if)

So how can I move the basic memory to #c000 (while the basic program is running)?
There's a system variable which indicates the starting address of BASIC. IIRC, it's at address #F676. So you could create a loader with a starting line like this:

5 ' Autoexec.bas
10 IF PEEK(&HF677)=&HC0 THEN 40
20 POKE &HC000,0: POKE &HC001,0: POKE&HF677,&HC0 ' Move BASIC to page 3
30 RUN"Autoexec.bas" ' reload and run myself at new BASIC start address
40 ' ...rest of program goes here...

You can of course combine lnes 10-30 into one oneliner.
This format gave me the opportuniy to include some useful (?) comments

Again a question regarding basic: If I use Auroras program, what is the maximum amount of bytes I can load with BLOAD (starting from #8000)? Seems that 31KB is too much.