To the first thing: Yes, that is a bit more complicated because there is a lot of magical pieces to look at and it is different for NPC and PC (due to the different design of their sheets; there is less track of magical bonusses in the NPC sheet and so FG does not know where the bonusses are coming from). What I actually have is the following:
Attachment 27391
It is only a prototype, so it looks a bit ugly at the moment :D There is some new toggle on the very right at every entry, that is for antimagic. The plus means "no antimagic", the minus means "antimagic". (I may change that picture for that button when I would finally find something which would be allowed to be used :) Like a magical wand which could be turned on and off. And it is not on a nice place at the moment because everything is shifted to left such that the headers on the top are not fitting anymore; as I said only a prototype) What it does: Every effect with the string "MAGIC" in it will be turned on (when "plus") or off (when the "minus" is there). But one can still manually change the "on/off" toggle of course :) So it is like a group on/off toggle for all magical effects
But yes, then I realized that it would be a major rewrite of NPC and PC sheets since all magical effects which are not effects in the CT have to be tracked and turned on/off (i.e. ignored) with the antimagic toggle. I am not sure yet how the design of that should be and therefore I refused to upload the thing I already have since the extension would not be complete :) But maybe one would be already happy with that antimagic toggle in the CT and the feature of having all magical effects in the CT turned on/off?
To the second and third point (since they are somewhat similar): Yeah, I thought about that, too :) (in the thread about save versus tags I wrote some future ideas in the second post, I guess) But also here I am not sure about the design yet. When one casts there are many possible ways to do and a lot of things are happening. Cast button, save button, CLC and so on which are triggered separately or all whole together by the cast button. Immunity has to break every action then somehow by sending a message into the chat about that someone is immune. So I would have to carry over the information about the tags (which is already be done for the saves, so I know how to do that) and then it is now also checked for an "immunity" string. I guess that should be possible somehow :)
To the fourth point: Yes, that should be easy to do, I guess :) Maybe already the next thing I am going to do if I should stop the antimagic stuff for some while :)