@Dan, that functionality was removed recently. It produced odd results so has been restricted to the preset phases.
@Rex, not all of them, but a bunch of them. Notably the ones that either seem interesting or align with stuff I'm working on. Some of the suggestions are actually just additions to some of the cards I'm working on (like Leon's Explosives one, it's really just a weaker Nuke, so really easy to make that).
StereoTunic9039 is creating some (he's considering the Retry Card suggestion and he's making a Landmine mod now). Dutch makes stuff all the time so think he's too busy on those to implement these changes.
Following are the one's I'm working on & will publish in the Custom Card Package A mod. The first 3 are refreshes of dabo1's Custom Card Package mod that implements Nuke, Pestilence, Isolation. I'm updating them to be proper cards, upgrade the the UI so they're easy to use (Nuke can click on territories to activate instead of selecting territory name from a list, etc).
Done / final tweaks in the works:

Working on next:

Working on in the future (after first release of the Custom Card Package A mod):

So if there are any suggestions which are essentially variations of any of these cards, where it makes sense, I'd just add a configuration option for that - like making the Nuke card fully configurable to activate in a different phase. Default will be BombCards phase.