Those are great ideas! Our first game has been pushed back until May; we'll probably go rules as written for that and then see what we want to tweak after that.
One thing that occurs to me (not least because I just uncovered a whole load of partly painted Renaissance-era fighters that I'd been prepping for En Garde a while back ...) is that Mordheim could possibly do with another type of armour. So rather than just light and heavy, you'd have light (6 save), heavy (5 or 6) and full plate (4,5 or 6). And of course, full plate with shield would be 3, 4, 5 or 6.
I can see a few advantages in that. First, we know it works (think of space marines in 40K). Second, it models the sort of armour that Citadel miniatures tend to have more accurately. Is that orc with a long hauberk in light or heavy armour? What about the guy with a padded jack? What about a mail shirt with vambraces and greaves? And third, it means that your 'tanks' with full plate and shields will have a decent chance of getting through a volley of missile fire.