So...don't level up

? At least, with bounded accuracy, that seems a possibility.
... I want to get better as a sage. This can't possibly be a real reply, can it...?
Honestly, that sounds like a campaign option to me. Trying to fit the kinds of things your suggesting into one party and still make a viable campaign would be very difficult under the general D&D framework, requiring constant DM-intervention with the rules.
Thus, it is "optional" with the default as "balanced."
Hard to evaluate without knowing what kinds of non-combat abilities we're discussing. I generally like 5e's "bigger" units of character description rather than the significantly smaller units of 3 and 4e. I certainly don't think the must be on the same schedule as feats, although possibly they don't need to be on a particular schedule.
If they aren't on the same schedule, then I don't think the "get another background/talent by losing specialties/feats" is an appropriate answer. And if that's not doable or appropriate, then I have an objection.
Siloing has far too many benefits to ignore or discard as a design principle. For instance, if there is a dedicated non-combat silo, you could alter the advancement of that silo in your game independently of the other silos. Some suggestions have already been floated in this thread. So siloing could still allow some of the concept diversity you desire. On the other hand, non-siloing makes a great many other character concepts unworkable in many groups.
Dude, I feel like I've addressed this over and over. You
replied to my take on it in your post that I'm responding to now. Make the move away from siloing optional. Make everything "balanced" as the baseline.
But give me the option (with mechanical support) to change it to something else. You never, ever have to leave the baseline, default, siloed approach to the game. Everything will be "balanced" across the pillars for you from the get-go. Awesome.
Me? I want mechanical support if I want to alter those assumptions. Other people do, too. Give us that support. Just design background/"talents" just like you do specialties/feats, have them run simultaneously, and I'm fine with it. If I can't switch out my Intimidation skill for more punchyness, or my fighting skill for more knowledges, etc., then you're killing my concepts. Yours live either way. Yours are even supported as the core assumption. Just let there be support for mine by not
forcing siloed abilities. As always, play what you like
We're just talking in circles now.
Seriously...
the idea... is that the default would be that you pick your "feat" at certain intervals, and those would primarily be combat based. HOWEVER, we could also leave in the choice to pick one of the options from the other pillars, with the knowledge that this won't have the same mechanical contribution as the combat feat.
Yes. This. Clearly explain that this is the case. Make sure it's noted that it's not appropriate for certain campaign styles or expectations. Etc. But let things be swapped away from the baseline assumption. Please, do what the bogmad says. As always, play what you like
