That kind of thing won't happen, ever. Tiger elephant stugE etc all in the same doc.
It will probably be an advanced, upgraded version of the bulletin system.
The point isn't the specific combo, the point is that no matter what system they pick, they're going to have to price the abilities. Some are going to be worth more, others less. That learning curve for them is going to be painful for us.
For example, some folks have proposed permitting one epic, one rare, three common abilities. Well is a Tiger epic or rare? Others have proposed a point system--10 points total, are p47s 5 points? 4? How about air supremacy? Basically all the upper ranks who are aware of abilities that are powerful but currently undervalued by the meta will throw them together, and its going to suck. While relic is working out its structure we're going to be dealing with broken-ass combinations. No thanks.
Even aside from those issues, there is simple readibility. Doctrinal limitations add depth to the strategy because you're forced to choose--do I use an early ability and reveal my lategame? Or do I hold off and forgo the advantages of my early CP abilities? When anything goes with anything, that readability goes away (God help you in team games if you've got to memorize five abilities for three doctrines for four enemy players literally every game.) Custom commanders kill that strategic depth in return for a dumb gimmick.