It occurred to me that this could be implemented in Oblivion by changing the names and descriptions of the skills, perks, and so on. I've actually made an experimental ESP that does this most basic part of the job. I set up Blunt as "two-handed" and Blade as "one-handed". The next step is simpler but much more time consuming: All type "onehandblunt" weapons in CS need to be reclassified as "onehandblade", and "twohandblade" weapons have to be reclassified as "twohandblunt".
At this point you have functionally duplicated the advertised Skyrim system.
The trouble comes in a heavily modded game. Patching for this would have to be a nightmare - in order to make sure that no other mods changes to weapon stats, models, etc., were overwritten, while the change in weapon type was implemented without fail, you'd basically have to patch every file that adds or alters weapons. Certainly this could be done, but it's a whole lot of work for one person. I estimate that just doing it in my own game, in the simplest possible way (directly editing with TES4EDIT rather than making patches) would take 15-20 hours of my time - I have about 300 mods in total.
It seems like this should be simpler. It occurred to me that this could be implemented as a Bashed Patch tweak, and I've already put in a suggestion/feature request with them. But does anyone have any other ideas or expertise to offer? How would YOU do it?