Yep, I like that as a solution !
I always worry that Perception rolls (or Spot rolls in 3.5) are made too frequently. I appreciate that's why 5th Ed bought in Passive Perception, but that's a mechanic I hate because I've seen it misinterpreted or abused too often.
So for the majority of the time, I view anything that happens as either so obvious anyone could see it, or so discreet that a character has to ask a reasonably specific question for a purpose and then roll for it. Not "as I walk down the road, do I see anything odd ?", but rather "as I walk down the road, is there any fresh night soil, or does it all look more than a few days old ?"
I am 100% with you on that! That's why I enjoy passive perception and insight, but some feats like Observant...Observant can be great, I often say to the player he can roll perception or take passive from observant if it is higher or he feels one applies more rigorously than the other. I guess what's difficult is being on watch at night. Like, I think that I'm working towards is a better way of handling the night time watch, maybe making CON saves to stay awake?
I've always been really conflicted about the night time watch system. On the one hand, it's a good way for a DM to mess the party up. But the reality is that unless they are on a time-sensitive mission, most parties then just have a rest day to get their spells etc back, so all it does is slow things down.
Nowadays, I ask that the players set up a standard watch rota at the start, and then generally let them have their rest unless there's a good reason in the storyline not to. But then I mostly play 3.5 rather than 5th Edition - unlike 5th, with it's Long Rest mechanic, 3.5 is more about spells returning at dawn but only if you've had a full night's sleep (that's the simplified version, of course...)