This army list reeks of Warmachine and it'd play like a Man-o-War list.. which is bad in
40k given that you'll most likely run it in a brick formation to get the most out of their defensive capabilities.
My main issue with them is that you're most likely to get outmaneuvered by pretty much anything. A few things come to my mind that would ruin your day - Tau gunline, Eldar, Riptides and while they basically ruin ANYONE's day another big problem is.. the same codex you're using, ironically.
With easy access to tanks in
HQ slots it's easy to have 3 Manticores in an
AM list, leaving you with 3d3 S10 Ap4 barrage large blasts that will evaporate your ogryn brick in one or two turns. And if that doesn't remove them from play, 2
LR punishers will cover you in such a generous amount of multi-melta, punisher and lascannon shots that there will be nothing left of your force, tabling you turn 2 or 3.
That being said it looks like some fun little project and I'd love to see someone play that, even just for the majestic lulz!