Very true. I don't pay your sub.
You can post pretty much any suggestion in here that you like. That being said, it probably makes more practical sense to come up with ideas that don't simply completely replace DRK with a completely different job, real or homebrew. I think that this is a good rule of thumb for any job design change.
The reason why I've posed this particular challenge in here is for a couple of reasons. First, this is perfect timing to start thinking about what the next expansion will be like for DRK's gameplay. Second, it challenges you to think about how the addition of an action can interact with the existing toolkit in unique ways to in order to create a significant change to playstyle. This is actually one of the things that I think has been pretty smart about BLM's design over the years.
The three action limit that I suggested is based off of what we've actually seen this expansion in Endwalker. We've also seen them trend away from removing actions and towards upgrading them to keep action counts constant. DRK has been a bit behind on the action counts compared to say PLD since Stormblood, so there's probably still some room for a couple of new actions. But who knows, they might all just be animation upgrades.
I will say that I have seen a number of job action ideas bounced around on the forums and ultimately make their way in game shortly after, so either there's a lot of lucky coincidences going around, or perhaps they do look at some of the feedback in here.
At the end of the day, this is still a challenge, which means that it's been entirely optional from the moment I suggested it. I've done this sort of suggestion thread as its own separate thread each expansion since Stormblood (wait, that's not Ingress/Egress in there, is it?), but since there are so many volunteer job designs in here for DRK, we might as well carry on that same momentum in here.
You don't have to follow the constraints that I've suggested, but I think if you try them out yourself, you'll come up with something stronger and even more interesting for it.