Hey all, looking for feedback on a homebrew ability to adjust balance for my Warlock in my Eberron 5e campaign.

Some context:

Our campaign structure is very different from the standard dungeon crawl balance that 5e caters toward. Instead of multiple fights per day, we typically have one or two big, plot-heavy battle every few sessions, with long stretches of exploration, investigation, and social encounters in between. Sometimes there are a few smaller skirmishes before the big fight. Short rests rarely happen because:

• There's often no in-game reason to short rest. We aren't in hostile territory, and there's usually no urgency or reason for the party to sit around for an hour after a single fight.
• Only one party member (the Warlock) needs short rests. Since the rest of the party is fine relying on long rests, they naturally push forward instead of waiting between fights.
• Combat is sparse but significant. When we do fight, it's usually a major battle that pushes characters to their limits, rather than many encounters in a single adventuring day.

Because of this, our Warlock is often much more limited and picky with when to use spells, since they're balanced around regaining spell slots on short rests. Which, in this campaign, just honestly don’t happen. This means that sometimes the Warlock holds off on using their spells, to the potential detriment of the party, because there's a higher risk of "wasting" a really limited spell slot too early. While combat is sparse, I think there's always the fear of "but what if this is wasted for the day and something comes up?"

All that said, I'm considering a homebrew ability similar to the old Warlock Life Tap spell from World of Warcraft, essentially letting them trade health for spell slots.

Here's the direction I'm thinking:

Homebrew Ability: Dark Pact

As an action (bonus action feels too strong unless the HP requirement is very steep IMO), the Warlock can sacrifice twice their level in HP (or a % of HP?) to regain one expended spell slot.

• This ability can only be used once per long rest (also toying with the idea of = to proficiency bonus).
• (Unsure if this should also be included) If this ability reduces the Warlock below half HP, they suffer one level of exhaustion.
• Would always take from HP, can't use Temp. HP for the sacrifice.

My goal is to give Warlocks back some of their spell flexibility while making the cost high enough that it’s a real trade-off. But I don’t want to break action economy or making the Warlock too strong by giving them more spell slots than ever intended.

Does this seem fair? Should the HP cost or restrictions be adjusted? Has anyone else dealt with short-rest-dependent classes in long-rest-heavy campaigns and made homebrew adjustments?

Any feedback would be much appreciated! Thanks for reading to the end.