Let me change what I said before slightly and elaborate a little bit more... Certain things modify a stat directly (furious charge / Power Fists & Klaws / Ork mob size) but all of these have a built in limit to 10 in the base rule set. You can not modify a stat past 10. That being said there are times when you get modifiers which do not affect the stat directly but are added in to be used such as getting additional attacks for 2 CCWs, charging, daemon weapons and in the case of LD you have positive and negative modifiers to the test but not the stat directly. Again I also point out to you that GW does not test their rules with rules lawyers to see if they can be broken. Most long time gamers understand that certain rules where not meant to be broken even if GW screwed up some minor wording.
I think this is the best answer that we can get without contacting the trolls at GW. Using the RAW this is what I get from it as well.