Yeah, I don't blame you at all; Spectranet is the perfect interface for deploying cross-compiled code to a Spectrum I reckon - either through a local TNFS server, or that handy 'Load arbitrary data to RAM' in the NMI menu for machine code routines. So you can take advantage of modern development tools, and still test/enjoy the results on original hardware - why wouldn't you?! (The Oliver Twins built their Spectrum games on an Amstrad, isn't that right? That's kinda the same thing…).
Have you tried zmakebas? I haven't tested it extensively but it seems to work for me and doesn't complain about the % commands (though it might be treating them as NextBASIC variable names, I'm not sure!).
Anyway, thanks for the details, you've given me some fresh ideas for my own site - cheers!