Greetings, I'll try to make this concise while also providing as much information as I can.
I found that the spell 'Clairvoyance' was completely useless in Skyrim, yes I suppose while dungeon crawling it may make things a bit easier but it didn't really do anything that map markers combined with the map couldn't provide just as easily.
The premise of this mod idea is simple. There are many mods out there that remove map markers, I'm simply suggesting map markers that could be 'activated' by clairvoyance.
To clarify, the effect of clairvoyance would be changed to a toggleable spell (That could reduce your maximum amount of magicka if you feel it appropriate) which would enable/disable map markers.
If you are unsure on removing the current clairvoyance spell from the game, you could always simply add it as a new spell instead.
In fact, you could even have multiple levels which would appear at the regular vendors when you reach the required illusion skill level, for example:
Novice: Clairvoyance (Vanilla Effect)
Apprentice: Clairvoyance Toggleable (Toggleable Vanilla Effect)
Adept: Clairvoyant (Toggleable Map Markers)
Expert: Master Clairvoyant (Toggleable Map Marker and Vanilla Effect)
Of course if you do this you'd have to find a way to make it so you could only activate 'Clairvoyance Toggleable' or 'Clairvoyant' to make the 'Master Clairvoyant' spell worth getting.
(Or I guess simply make the 'Master Clairvoyant' spell have a smaller magicka drop than the other two combined if not)
Anyway, I hope that is explained well enough for anyone who is interested, if not feel free to ask.
Non-Modders also feel free to suggest ideas or alterations you'd make and of course just generally let me and potential modders know that you are interested in the idea or if you have any criticisms.
Thanks in advance for any responses.