I think you might be bringing normal lore into TES lore with the sunlight stuff since most vampires burn but for some reason they don't when they are fully fed....kinda odd but I agree.
What I used to do in MW was wear full body armor and stuff so that they would not notice I was a vampire since they could not see my face and I wouldn't burn in the sunlight, see I did this till I realized it didn't work lol...
But ya I agree, I would think get stronger when you do FEED alot with help from perks and such than get weaker when you don't and when you don't feed or someone sees you feeding you won't be able to talk to some people for awhile cuz they would know what they are so you might have to stay out of that town for a few days till they just randomly forget.
And sunlight should still hurt you otherwise vampires would be over powerd, so ya if you are wearing full clothing or armor that covers your skin that would work so that the more armor covering or whatever the more chances of you not burning to death fast since I highly doubt you will get a full suit so that you don't get a touch of skin to burn XD