My concerns with spell points, especially recovering spell points on a short rest using your suggestion, is that casters are way more powerful all day. They no longer have to have a long rest to recover spells, ever. Long rests are only for recovering special class abilities and exhaustion. They get to do way more cool stuff more often as a caster than martial characters get to do. It seems to me that you would really have to change everything about martial characters to make them compete with spell points.
As mentioned earlier, the level+1 points per Short Rest, roughly equals the Warlock.
No one thinks the Warlock is too powerful.
Let's say you're a 7th level caster. You have 8 spell points. You can cast eight 1st level spells every short rest.
Sure, a level 7 caster can cast 8 level 1 spells before needing to find a 1-hour rest.
But then that means, no Fireball, no Fly, no Counterspell, etcetera.
How to spend the points is a fair tradeoff, and a tough dilemma.
And what is to stop you from having 5 short rests per day in a dungeon environment, blasting 10 fireballs throughout the day?
5 short rests per day? In a dungeon environment? As a DM, I laugh at the naivete!
In my experience, players are likely to get 1 short rest per day. 2 rests if they are fortunate.
The problem with Short Rests is, when they need them the most (stuck in a dungeon crawling with hostiles) is when they are least likely to get them (because the hostiles leave no safespace and interrupt attempts to rest).
Oppositely, when they are camping out in the middle of nowhere and there is no one around to fight, they can have as many Short Rests as they want.
Just keep pushing. Clear an encounter area, shore up defenses for a short rest, recover all your spells, then push on to the next area.
"Just"
Shore up defenses against intelligent hostiles who now know where the players are, and are sounding the alarm?
Lay a 24-hour siege where you never take a long rest until you clear out the dungeon. If you really need to, cast Leomund's Tiny Hut which you can return to as your siege base for short rests.
Have you or your players never had your Hut surrounded by hundreds of monsters waiting for your spell to end?
Also, if you are advancing levels via XP, you advance way faster from day to day because you rarely need to stop.
I dont use XP. I just count the number of encounters until the next level.
Heck, at 7th level, the bard gets all their best abilities, like spellcasting and Bardic Inspiration, recharging on a short rest. They never really need to stop unless they get wrecked with Exhaustion.
Why play a warlock who only gets two 3rd level spells with no flexibility? I suppose you can make warlocks follow the same spell point rules, and take away one of the things that makes them unique.
The Warlock gets always on Invocations as well as spellcasting.
I suppose the designers could add a gamist rule limiting short rests per day. But does that fit the narrative of all worlds as a core rule?
To be fair "slots" are the "gamist" rule that dont really make narrative sense.
Oppositely, having a certain amount of "energy" that runs out as one casts spells, is pretty much how most novels and films describe spellcasting.
At the end of the day, I wouldn't use that short rest spell point system unless I wanted a very specific high magic story-driven, milestone-based campaign, like Strixhaven, and everyone had magic. That is why I think spell points should be an optional rule, which they are.
No one is complaining about the Warlock class.
The classes that people complain about are the traditional spell slot classes, especially Wizard.