Hi,
More metapackages will make transitions harder though, I believe we want to avoid that.
In what way would transitions become harder?
The alternatives system has "manual" and "automatic" modes for each group, these would probably correspond to "manually installed" and "automatically installed".
The latter can only happen if there is also a "defaults" package that pulls in the metapackage we currently designate as default, and the "defaults" package must allow the dependency to be fulfilled by any of the choices. APT will prefer not to uninstall packages if it doesn't have to.
As a result, any user will stick to whatever was default when they installed the package, even if they have not explicitly expressed a preference, until that option is no longer available -- the same happens with the alternatives system only in manual mode, which is an explicit choice -- and when it happens, the alternatives system will explicitly tell the user that their choice is no longer available and the setting has reverted to automatic mode.
The only way to speed up a transition is to add an explicit hard dependency somewhere and override the user's choice -- which then adds an installation ordering constraint that might be the exact opposite of the order we want.
Simon