What is Overflow was a choice? That is, you have impulses where you could expend your gathered element for greater effect?
As an example - Aerial Boomerang. Make the return strike happen only if you expend your element. Tidal Hands could be set up as either the AoE or the damage is from overflow (that is, without overflow it gives you a single 15' cone, with overflow you get to choose its current flexible shapes. The other option is a more straightforward "if overflow, use d6 instead of d4" format).
This still doesn't completely address the issues of damage on impulses, as many of them would still underperform currently. It also allows more specialization in impulses, since you can have increased damage on some, increased AoE on others, etc. to make them attractive for different purposes, whereas right now a lot of them feel like it's just "how much does this hit for".
Other options:
Hurtling Rockfall - make it deal X damage to everything in the area. Overflow causes additional damage to the primary target specifically.
Flame Eruption - Make this deal 2d4 (+1d4/2 levels) in a 5' burst/30' column, with the current hazardous terrain. Overflow condenses it into a single 5' square, but the column is twice as tall and you use larger dice (i.e. you've compressed the explosion).
It's possible that some impulses might remain overflow-only? The level 18 ones in particular come to mind here - some of them (Ignite the Sun, Crowned in Tempest's Fury) are kind of a big bundle of effects - the only issue is balancing them to be worth the action cost, but it's hard to decide what you'd make part of overflow or not. (And I guess overflow on something that's already 3 actions is a lower cost than on 2?)
This does get into some interesting questions though with existing feats. Cyclic Blast at 6 actually negates the cost of overflow to a degree, since it's basically Quick Draw for kineticists if you choose to do Gather Power>Elemental Blast (also, as written you could actually use the element you just overflowed this way, but) to do a standard Strike>Cantrip type turn. And of course overflow isn't much of a cost if you were thinking about swapping element anyways because you're a multi-element build and want to bring out something different. Both of these, however, don't apply to Dedicated Gate, which doesn't get any mitigation of overflow until 19 (kind of just reflects the issue of overflow more than anything, and my proposed change makes the playing field a little more even there I think)
Edit: Further variation! What if each gate had its own overflow you could always use? E.g. dedicated gate gets Overflow: Increase the die size of a blast by one step. Dual Gate gets an overflow that lets them change to their other element (so rather than empowering that impulse, it removes the action cost they'd normally incur in swapping elements, letting them use both more freely). Not sure what I'd do for Universal gate? Edit 2: Swap damage type of the blast out maybe? A focus on flexibility... though it still feels like it may be iffier on its own.
