As stated (and it should have been immediately evident for someone as learned as you), all of the "financial gimmickry" would not have been possible had interest rates not been so low for so long.
EVERYTHING that has resulted in the recession we are now in goes back to the Fed, whether it be guaranteeing Fannie and Feddie or providing nearly free capital. Higher interest rates would have prevented a lot.
Again, the interest rates had almost nothing to do with it. Almost all of the gimmickry was designed to circumvent interest rates. 5/1 ARMS were designed to have low interest rates for a short period, locking in the shortest period of the yield curve (and the least spread-ey). Even if rates had been jacked up, the 5/1s were still done and locked in.
Option-Arms were designed to circumvent ANY interest rate increases, considering that you had the ability to capitalize a cumulative 25% of coupon. That means that even if the Fed had jacked up rates, it wouldn't have mattered.
Liar Loans were designed to not even tie affordability to the mortgage, thus, who cares if you could afford the interest rate?
On the funding side, as mentioned above, the market had their own version of Option-Arms in PIK toggle notes. Risk spread compression was abound.
The only theory that comes even close to explaining the boom is that low rates in Treasuries, as a by-product of low FF rates (although I don't buy into it since they are different products), resulted in yield-chasing to RMBS and other products. This is a silly argument as long-term rates aren't set by the Fed, FF rates have limited affect on LT rates when a bubble is in full blown frenzy mode.
As far as the GSEs, the guaranty was always implied but never explicit. The GSE's proportion of the mortgage market actually DECLINED during the bubble.
Seems to me you love reading Austrian FUD but know very little of reality.