I would prefer guards of different ranks...

In the Thief series there were alot of 'idiot' guards who were easier to sneak past/kill/evade and there were more 'well trained' guards who you didn't want to mess with.

And they all had fantastic and varied dialogue.

i would enjoy archer guards. the stealth ones may be kind of OP. i think mages is a little rare unless you're F-ing w/ the mages guild.

As long as they all have their stock mantra ("Stop right there, criminal scum!") who cares?