Thanks for the replies folks, great to see so much enthusiasm!
Ron, I've been following the progress of the Dragon version, I'm bowled over by what has been achieved (and by Kees' work on the Atom too, for that matter) and am in regular contact with Kees. The Dragon shares a graphics chip with the Atom so there are monochrome editors for that and the Atom, I'll be starting work on colour mode editors for the Atom and Dragon soon.
Geco, that would be wonderful! You're welcome to the source code, it's included in the latest download at my site as part of the zip file. The compilers you'll be interested in are CompilerZX.c and CompilerCPC.c and the engines are EngineZX.asm and EngineCPC.asm. The engines are fully commented although there's a slight typo in the CPC engine, the second xorbk0 label needs changing to xorbko. The Amstrad's screen width didn't really match the Spectrum so I had to resize the blocks and sprites so that games could be converted between the two without any major issues. Take a look, let me know what you think. Maybe take the best of both?
Endi, the Spectrum and CPC need specialist engines for scrolling so it isn't incorporated in those but there's no reason why it couldn't be added as an extra in the Enterprise version. That said, there is an up/down/left/right starfield option for shoot-em-ups.
GFlorez, Absolutely.