So playing A17e for quite a number of hours I find that I really miss leveling on use.
I also like the rpg system of A17e too so I'm wondering if they can be combined.
My thought is that levels of a skill are also progression gates for leveling the skill.
So if mining level 1 adds 10% to the amount of resources collected instead of automatically jumping to 10% for mining it allows you to progress to 10% in mining, as you mine you level up to the 10% gate that Mining level 1 allows.
I also think there should be a little bonus for reaching the max gate from each level.
So if there are 5 levels for a total of +50% resources, you would get a small bonus at 10,20,30,40 and a special bonus at 50.
Level and/or Master attribute gates still apply.
This could be applied to almost, if not all, the skills (gun,tools, armor,etc)