Sure, you can do whatever you want.
The thing is, when we feel the need for the PONR stack (no matter which “generation” we’re using) we’re often not in the most receptive state for other fields. At those times, our challenges (and our attitudes and reactions to those challenges) prevent other fields from helping us in the ways we read about here on the forum.
Think of it as living in a messy room–a really messy room, like a pigsty. Sure, you want to live in a nicer room. I get it. But with an actual room, you understand that you just can bring new furniture in a long with the old furniture and you can’t lay new carpeting down on top of the old carpeting. You know you’re much better off when you first clear out and clean your room, and then bring in the new furniture and carpet and fresh paint.
Can you play new fields? Sure.
Might you have cleaned out your room enough for them to work? Maybe. Or maybe they’ll just work a little slower because you haven’t cleaned out your “room” enough yet with your PONR. None of us can say for sure for you, because we’re all different.
Now, the fields you’re mentioning really are separate from your “stack” (in terms of their goals and operation) so you can play them separately from your stack. Because they’re separate from your stack, there’s no added benefit for you (beyond, maybe, convenience) in adding them to your stack.
Play them at the end of your stack or give yourself a little break and play them at a different part of the day with some of the assisting fields from the How to Create Great Stacks thread.