I intend to do my best to ensure that things don't break, but I need to fully understand how modules are meant to be built, and I need some to test with. I guess I can download a few using pike -x monger. Then I'll probably have to test building and installing those modules manually before releasing a new Debian package.
We need a Pike Policy for Debian.
For starters, third-party modules can't be installed in the versioned modules directory or such packages would have to be rebuilt every time pike is upgraded. If a module is built with Pike 7.6.x, it will work with all later 7.6 versions, whether it's a C Pike module or a Pike Pike module, right? We clearly need counterparts to /usr/lib/perl5 and /usr/share/perl5 for packaged modules, and dynamic_module_makefile should support $DESTDIR.
Locally built (not packaged) modules should be installed in one of the directories in /usr/local, however. Maybe use the install_local target for that, and patch local_module_path in module.pike to e.g. /usr/local/lib/pike7.6/site_pike.
The second problem I think I already addressed: Only stable Pike releases should be uploaded to sid, possibly with a few isolated and well-tested patches.