I'm all for sticking with the models. Im not suggesting blowing anything up and going with new models. Legendary in the last line on his last post said balance standards are perfect as they are. They might be very good, but common sense says they can't be perfect. How many items exist that break the model? I'm not even talking builds... There are many. Example- Luck has 10% rate for lucky strike. The model includes this. But if you regularly cast arms of dragonguard, especially with celerity from shadowfeeder, there's no way the model gets maintained. I'm not advocating for change here, I'm simply pointing out you can break the model if you decide not to use the same bland equipment with little effects of yesteryear.
Arms of the Dragonguard takes a 40% damage penalty, worth 80% melee, in order to increase your critical hit ratio to 100%. Shadowfeeder Pendant enables you to pay SP to attempt to gain an additional 140% melee. In both of these scenarios, you sacrifice damage (from the player damage and SP components of the player turn formula) in order to gain effects that help you increase your damage in other ways. Within this context, both follow the model (Here I make a simplification because Dragonguard isn't technically balanced, but it has been designed with the intention of following balance and so I see this as irrelevant). In other words, this is not an example of breaking the model.
A better example is Essence Orb. It followed an outdated concept of HP costs based upon damage intake. 75HP was worth ~50% melee, the equivalent of 196sp. Multiply this by 0.9 (an always useful penalty that was on standard) and you get 176.4SP. Balance was intentionally broken, applying an additional *0.5 penalty because the Staff considered it to be too powerful. This resulted in the 88SP that it currently heals. This is deliberately unbalanced. It's also unbalanced in the new system, where it would be worth 75*0.9*1.125 = ~76sp. It wasn't balanced then, nor is it balanced now. Of course, neither of these scenarios are the reason why it needs nerfing - it's because we can essentially gain multiple bars of SP with little to no effort. That's why it's at the top of the list for nerfs.
The mage has two ways to play. Cast spells and use guests, using guests for less turns. Or just use guests, longer. And MP heal is not only stronger (1.5 vs 1.125), but more plentiful. Just potions alone.
Having access to MP for upkeeps (guests/miscs) and saving SP for other things already expands it's versaility far beyond the beast warrior who now cant heal SP the same.
Please reread my previous comments about being wary around comparing MP to SP. You are certainly correct to say that beastmages are able to use guests that cost SP and MP. However, MP heals are not directly comparable to SP heals, and they are not stronger. They are more plentiful, but this is because Mages use MP as a direct source of player damage. To equate this to a warrior, it would be like creating a guest that, as a cost, reduced player damage output by 30%.
There is no sound argument on the planet that would cause me to change my mind on that. And I don't even have the "math" to say otherwise. Even if it did show otherwise (I'd be shocked if it showed beastwarrior vastly outclassing beastmage) It still doesn't account for real life gameplay with real items, that do and will break models.
So, IMO, warriors need a small amount of SP help.
Here, you cross into the territory of the other issue I warned of - constraining this to a dichotomy between Warriors and Mages. SP is a universal resource. Rangers and other builds require solutions here too. Moreover, closing your mind to counterargument (even if that argument isn't well-founded) means that moving forward with this discussion becomes impossible.
Once again, nobody here is arguing that mages have increased versatility as a result of storing their damage as MP. We don't (yet) have many non-mage methods of utilising their equivalent resource. MP will somewhat shelter mage builds as SP regenerating items are brought onto current standards. With that said, non-mage builds are gaining preferential access to SP regeneration (the primary subject of this conversation doesn't even regenerate SP for them). This isn't balanced - SP is universal and technically builds should have equal access. However, it's fair due to the power balance we currently see. Non-mages need that advantage to be competitive right now.
I'll also interject with a (potentially) controversial opinion. The reason FO non-mages want access to this kind of SP regeneration is to regularly nuke their opponents. However, I would argue that, since mages are designed to offload damage inefficiently at the start of battle, they should inherently be better at nuking than other builds to begin with. Non-mages wanted to copy mages due to it being the meta, resulting in a slew of inefficient non-mage nuking items such as bloodzerker (again, let's gloss over that mages can use these). If we are to regain a sense of build identity, Non-mages shouldn't be attempting to copy mage (e.g. by having SP become a build-specific bar), but instead, focus on doing what they do best. Perhaps for warriors, this could be a focus using SP to deal decent damage efficiently, rather than high and inefficient strategies of mages.