So the added metabolism is a great first step towards a more challenging early game.
I think that shelter should be the next development.
For example… exposure becomes very dangerous at night, and the building plan should be a lot more expensive or even not craftable at first. So there will be options of cheap shelters to build like in legacy. Perhaps the most basic could decay after just 1 night, with some more elaborate ones also. So it becomes vital to get a shelter up and a fire going before night sets in. Maybe you have to build a few shelters to get the correct XP to make the building plan?
If you don’t want exposure to be an issue in all biomes, perhaps wolves could even spawn near players at night, forcing you to be in a shelter until you are armed. Could be annoying in late game though.
I am imagining a game start where you need food and water quickly, shelter also, and with radiation back in there is no option to quickly find a radtown and get geared.
Would be a much more feral start to the game.
As a side issue, this sort of development will always bring issues for new spawns in established servers e.g. if you have to have a fire going to survive, you will quickly get gunned down by a roaming geared dickwit. Not sure what the solution is there.