Lvl 1 is only required to build all items (including T2) excluding the Standup Shadow Fighters. There is no tier system to progress the skillbook passed lvl 3.
For example a Titan requires capital construction lvl 5, so by expectation a Keepstar should require lvl 5 as well. T2 production should be Lvl 3-4.
It seems that low effort has been put into the purpose of the skillbook when Upwell structures were introduced into the game. With no tier structure established associated with the skill book.
Recommend a tier system is introduced, so that it fits more into the skillbook structure of the game and a reason to train it past lvl 3
Apart form that. You really expect that ccp gonna touch pos related stuff? And industry patch failure already introduced more pointless SP requirements. No need to add more just for sake of them being there.
Your idea of progression is interesting in itself, but there are 2 problems I can see.
Training time is too long. Keep in mind the Outpost skill is one of the x16 training time skills. It is one of the longest skills in the game, along with the 4 Titan skills… It takes an awfully loooong time to get to level 5.
CCP seems to not have any plans for changing the skill - well at least nothing they have said so far over the last few years. Some people have trained it to high levels years ago because it was used for Outpost construction before (hence the name). The skill was repurposed for citadel, refinery, and engineering complex stuff and eventually outposts were removed. Since then some people have asked about the skill, some people have also asked for skillpoint refunds, but CCP has kept silent on the skill.