Normally I like to run armor reds armor quints magic resist blues and health yellows however here lately I have been trying to um.. theory craft? What I'm asking is what is your opinion on magic pen reds on Braum? I understand taking the extra armor will be great combined with his w but if you were to be against a Ashe or a Varus (someone without a dash) could it work?
I personally use the same rune set up as you. But if I were to switch out the reds for Braum I'd use hybrid pen over magic pen. The hybrid pen would allow you to have a little more damage on your aa's as well as spells considering Braum is a tanky, in your face support. But alas I am only in bronze. Whenever I question if a build will work I always just try it out and see what happens. So maybe try out the magic pen reds in a normal and see how it works out with your playstyle.
I run rune page #5 : http://www.lolking.net/summoner/na/37465553#runes
I have found much success with it.
Whoa! Pen does work with passive! But if you miss your Q? you're just left high and dry with magic pen runes xD
I could see this working well in an 
comp
http://leagueoflegends.wikia.com/wiki/Braum
Upon reaching 4 stacks, the target is Stun icon stunned for 1.25 / 1.5 / 1.75 seconds and takes「 32 + (8 × Braum's level) 」magic damage. After being Stun icon stunned, an enemy cannot be affected by Concussive Blows.png Concussive Blows again for a few seconds, during which time they instead take「 6.4 + (1.6 × Braum's level) 」bonus magic damage from Braum's basic attacks and Winter's Bite.
