How about the Haskell Platform? Is that ancient history? Certainly not: it doesn't compile on anything but the very newest GHC.
I think you're missing the point of the platform! It is an explicit set of versions, including GHC, that make a stable reference set of packages on which to build, test, and deploy. Each version of the platform explicitly states with equality constraints the exact version of each component so that it will be the same for everyone.
You use the HP - with the GHC it comes with (or specifies) - as a set. You want to use GHC 7.4.1? Use HP 2012.2.0.0. Once installed you can install newer versions of the component packages if needed (though cabal-dev or cabal sandboxing is strongly encouraged in such a case to avoid "cabal hell".)
And unless somebody can explain to me how I would rescue my business now if I had opted for WASH
By patching it. Surely we are talking about minor changes here.