Which, in real world - considering amount of hands working on CSSU for real - results in limbo, that we neither get rid of mp-fremantle* nor get system upgrade packages (unreplaceable by other means, except for cp overwrite in postinst script - which is exactly why CSSU as separate repo got developed, to avoid such postscript ugly binary file replacements) incorporated into CSSU. See upstreamed and bugfixed busybox - for Maemo or CSSU, it exist in ancient and stripped version, while we have to install upgraded one via binary replacements.

Or theoretically great ideas like cssu-extra, that no one want to devote time on for >years (just because for all practical purposes, it's redutant, and manpower aspect comes again - there is always something better to spend time on, than this). No, don't even get me started on CSSU's package inclusion "policy" (buggy camera-ui vs. busybox-power, or only recently pardoned worldclock, anyone?).
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More on-topic:

int_ua, exactly ugly way to achieve what you want for modest-less system, would be to create dummy modest package that mimics real one (just empty), which version always higher than CSSU's one. It will stop mp-fre(...) from bitching and uninstalling itself. For calenda, say hi to method used by busybox-power -> binary replacing files via postscript, with layer of safety checks and backuping (as said, only other - and natural for this kind of package - method would be to ship it via CSSU, but <insert copy of paragraph one here>).

/Estel