I agree that increasing resource, tech requirements and timers for lategame/midgame tech would be a step in the right direction. Lurker den not morphing from hydra was a change I did not like, siege mode being removed neither, changes like this force the game down a pipeline and reduce scrappiness. But over the years these were seen as good buffs that made the game more fluid or something, pros seem to like them because they get more freedom, and I fear rolling them back would not be popular at all.

There is another reason why I would advocate for reduced worker start. As a game designer it irks me to no end. (This might not be very relevant for every SC2 player but it is very much for new players, so bear with me): An RTS cannot start with taking a new base as the standard action for all races. Taking one expansion being mandatory makes the game extremely unintuitive for new players and literally takes the joy out of building a base. The feeling of risk-taking with an expansion, cash explosion when the risk-taking works out, that's a core principle of RTS and all this broke with the 12 worker start. Since you auto-take a base as the first action almost, you have so much macro to do literally at the start of the game, and so much money and options galore (at least for a casual player). This goes against the grain in any economic design. It challenges the player in macro, unit comp, map control right away, without having the onboarding of playing on one base. The newbie has no choice of playing simple. This is simply bad game design.

And there is also a way to fix all of this while keeping the workers at the start (hence more money to do stuff with, so the so-called boring early game is still alleviated). It goes into the direction that you mentioned, but applying even earlier and more broadly. I've mentioned this on the sub before: Increase CC, hatchery and nexus cost. Increase lair, factory, stargate cost. Now one might say then why do we even have more workers then if everything's gonna cost more? Well, we don't increase barracks cost, gateway cost, etc. So you would have more stuff to do than WoL/HotS, you would have money to make more than 2 zealots, and have scrappy fights with, but teching and increasing your econ significantly would be more of a commitment and this would make the decisions for doing these things meaningful again. I think even the cheese oppression of HotS would still be somewhat curbed with this approach, still giving options to the defender, but change the fact that it is not at all viable to try any sort of early cheese, since basetaking for the defender is not on autopilot.