i'd prefer the namespace approach with some separation character that has a clear meaning and isn't otherwise widely used. e.g. / | _would be ok. Communication is always good but shouldn't be a must. There may
a namespace would definitely be a clean approach ... but someone will have to rewrite the build system ... the fact that single externals from the build system will cause problems ... there is also the problem with cyclone, since you don't know if cyclone is one cyclone library, or split to hammer, sickle and dummy ...
cheers ... tim