Supercheese
Zeppelin Commander
Specialist Enhancements
This (mini)mod adds <iHealth> and <iHappiness> tags to CIV4SpecialistInfos.xml, and naturally, allows specialists to affect a city's Health and Happiness.
This mod has essentially been done before, but I could no longer find an up-to-date mod that accomplishes the same thing.
Screenshots:
Spoiler :
Note that I was playing the Rise of Mankind mod when I took these screenshots; this does not mean this mod is restricted to RoM. It works fine in vanilla BtS, and in theory, with any mod.
It makes a world of sense to use this in conjunction with a custom Doctor (or Great Doctor) specialist that increases a city's health -- indeed, that was the main reason I wrote this mod in the first place (the happiness part is just an added bonus!

This is not a standalone mod, obviously... it is meant to be used as a part of a larger mod; please feel free to do just that.
Anyways, to the download links! I have uploaded it to the database: http://forums.civfanatics.com/downloads.php?do=file&id=13434
Note: Updated to v1.1: Added AI code (as suggested by Afforess)
Please re-download & re-compile the sources to update -- the XML has not changed.
The download contains the relevant sources, the required SpecialistEnhancements_CIV4GameText.xml file, and the altered CIV4GameInfoSchema.xml and CIV4SpecialistInfos.xml files. Note that in the included SpecialistInfos, no specialists have actually been set to alter health or happiness, just the <iHealth> and <iHappiness> tags have been added.
[Of course, adding the two clearly commented "SPECIALIST ENHANCEMENTS" lines to your existing CIV4GameInfoSchema file, and adding the <iHealth> and <iHappiness> tags in the correct locations to your existing CIV4SpecialistInfos file will work just as well.]
Anyway, that's about it. I do not plan on releasing a Doctor/Great Doctor mod myself. But as I said, feel free to use this code if you desire to make one of your own.
-Supercheese