Would a preset built this way be suboptimal or would a preset analyzes the image itself and short of the fine granularity of a slider, work?
A preset doesn't do any fancy analysis and is just a granular value (see below). If you really wanted granularity, you could have up to 201 dehaze presets to match the slider's -100 to +100 range.
Out of curiosity, I did look into whether one could create a small plugin with a Dehaze slider. One can do this for other adjustments but it looks like Dehaze values can't be set by plugins. That's probably not deliberate on Adobe's part - the Lr6 SDK hasn't been published - but I wouldn't ever release such a plugin.
John
Text of a simple Dehaze preset when viewed in TextEdit or Notepad:
s = {
id = "C5419DBD-95B0-4EAE-9955-0A977E9D1C22",
internalName = "Untitled Preset",
title = "Untitled Preset",
type = "Develop",
value = {
settings = {
Dehaze = -56,
EnableEffects = true,
ProcessVersion = "6.7",
},
uuid = "D62717D1-0BB4-4155-81F2-D0B8D1E39F39",
},
version = 0,
}