The 5e Skill list is one that I feel is missing a bit. I was thinking about adding
AD&D's Endurance (Constitution)
AD&D's Etiquette (Charisma)
AD&D's Law (Intelligence)
3e's Nobility (Intelligence)
4e's Dungeoneering (Wisdom)
4e's Streetwise (Charisma)
I don't see any problems with your house rules.
There are way too many people thinking that the skill system is closed and rigid, that every task must be covered by one and only one skill, that skill proficiencies must not overlap... they also forget that proficiencies are mainly just a bonus, not a requirement, unless the DM wants to enforce some difference between proficient and non-proficient characters (which I do, by the way).
When you change the skill list, IMHO the only important thing is that you should strive for all proficiencies to be more or less equally useful, so that taking one proficiency for your PC has more or less the same opportunity cost for the same benefit.
And how much a proficiency is useful actually depends on YOUR game. Only YOU can tell if a proficiency in Etiquette will be a good pick for a PC because in your games there'll be plenty of Etiquette checks, or those checks will make a real difference in the story.
While I am generally not a fan of Dungeoneering and Streetwise (IMO a bit too loosely defined and all-encompassing), they can be ok in your own games. It doesn't matter if they overlap with other skills, as long as they don't completely include them. For example, I wouldn't let a Dungeoneering check to replace a Thieves' Tools check in all cases, otherwise it might be better to just drop the latter from the game.
- Endurance is part of Athletics, you just need to make it a Constitution/Athletics check. It's easier to incorporate using alternate abilities than to add an entirely new skill.
- For most settings, Etiquette is best handled by Wisdom/Insight, as it's just about avoiding social traps. In a setting dedicated to crucial social etiquette, such as Rokugan or Kura-Tur, then Charisma/Performance seems more appropriate.
That's common in most games, and the reason why these are not 5e default skills.
But they could both interesting additions, for example Endurance is certainly not only physical... you might call for an Endurance check to stay focused on a task despite distractions, or to keep calm in front of others pushing you towards certain actions or emotions. Also, there are physical endurance "tasks" which are not really athletics, such as staying awake, resist hunger/thirst or painful wounds. The point of adding an Endurance skill is to allow a PC to
invest in such proficiency in order to obtain a
bonus on those checks, instead of using the default Constitution check.
What eventually causes some real mess is the co-existence of ability/skill checks and saving throws in the game. The distinction is mostly proactive VS reactive, but in mechanical terms they are both really the same kind of check i.e. d20 + ab.mod. + prof.bonus. So it's natural for people to come up saying "this should not be a skill check, it should be a saving throw" (or viceversa... that's after all why we still have 3 dominant types of saving throws, while the other 3 are rare because we have ability checks to escape spells that would otherwise have their saving throws!) but ultimately what matters is how a PC can get good at some checks at the expense of others.
For these reasons, I would
not recommend to think in terms of what "makes more sense" or "seems more appropriate" from a narrative point of view, when making house rules on the skills list, but instead I think it's best to focus on mechanical balance. Which, of course, is not very solid to start with, when you have a single skill for all Perception tasks :/
