The irony that is DCC RPG: A pre-D&D Sword & Sorcery Roleplaying Game built on d20, i.e. D&D.
But if you use d20 or d16 or d24 or d30 or d14 or d10 for actions, it is no long a d20 game. The hallmark of d20 (from 3e and d20 Modern to 4e and Pathfinder to all the other clones is the singular mechanic: Roll d20 add modifier compare against DC. True20 and Mutants and Masterminds takes that mechanic to the extreme, eliminating hit points in favor of a knockout "save" that relies on a standard d20 roll eliminating all other dice, including the d6.
If DCCRPG embraced the action die not being d20 90% of the time, it would not really be a d20 game.
I also like the idea of shifting this game away form being a d20 game. the d20 system is rather generic and, has been played for a long time. I really like how the funky dice, the action dice types, special dice for two weapon fighting, precentile dice rolled for thief skills, all help pull the game away from "d20+mod vs DC" mechanic. I even wish saving throws were based on the funky dice. The better your save 'bonus' from level, the bigger die you get to roll to make your save, for instance, instead of just a +1 level bonus. Inititiative bonuses from level could also be in the form of funky dice.
I have not read the previous threads in great detail here, but some of the examples I think can be handled fine with funky dice instead of normal dice just by having a well written rule with it. For example, a charge attack could allow you one attack with a d24 action die, regardless if you are dual whielding. It could read "When making a charge attack you only get one attack, even if dual whielding, using a d24 in place of your highest action die. Then, you may use remaining action dice as normal..." those kind of issues are just a matter of writting the rules to go along with it.
And I have to agree that comparing the d16 to a d20-4 in other systems is a bit of a moot point as the space between success rate with one style vs another in real life would be difficult to quantify, and so don't worry about it. I mean, no one has a proble with shadowrun being a d6 system and WFRP (the good editions) being d% instead of d20, so there shuldnt really be a problem with DCCRPG being a dfunky system.