(1) Would require a revamp of the entire economy. In the early game, 1000 copper is a lot of money. In late game, 10,000 is pocket change.
Well, yeah, making things cost money is only meaningful in a somewhat balanced economy. It's not really a huge problem if supply costs become less meaningful in the lategame, but you do indeed need to put some effort into this solution.
(2) Would only be a mild additional inconvenience (or a way to grind copper, if they dropped loot when they died). I.e., would not qualitatively change anything -- cost of too much resting is still inconvenience.
Not really. Respawns are an inconvenience, true, but they're also a resource sink. If you exit a dungeon to resupply, and then re-enter it, you'd lose some of said supplies in the process of getting back to where you were. This in and out of itself encourages better play, and then you can also introduce shortcuts into the level designs as progression milestones. Not really something IE-likes have tried in the past, but it is an option.
You laugh, but this year saw the release of Persona 5, a very successful (both critically and commercially) JRPG featuring TB dungeon crawling, which does this exact thing. The game takes place over 9 months, with each day acting as a basic time unit that lets you do things. Leaving a dungeon in P5 restores all mana, but entering it again costs a full day; and even with this, all enemies respawn so you can only really leave after finding a safe room if you want to preserve your progress.
So what you're really saying is that IE fans can't handle the hardcore mechanics of a mainstream weeb waifu simulator.
Main point is, I never once trekked back to an inn for supplies, but having limited resting and per-rest resources/per-rest health nudged me to pay attention to resources. I know I'm in the minority, and modern goons can't into that, instead simply resting after every fight and trekking back for supplies.
You crawled through the entirety of Od Nua without ever leaving?
So the irony is that P2 does improve resting -- but it removes the very things that make resting a worthwhile game element.
Well, if they're unwilling to make it meaningful, then might as well remove it and hope it helps elsewhere.
Personally, I just really like the idea that entering a dungeon in a dungeon-heavy game should feel like a commitment, a long journey you need to prepare for. IE games have never been very good at this unfortunately, and if Sawyer is afraid to innovate too much, then there's no point in half-measures imo.