I noticed Deadly Reflexes has these features but adds many others that a player may or may not want. There are also stability issues.

Would a modder be interested in just adding shield bash and duck to PC / NPC combat? Just the simple addition of these two elements would make for a wonderful addition to Oblivion combat without totally disrupting balance.

There are no issues with Deadly Reflex 5. Try that, instead of DR6. I've been using it for years without "stability" issues. You can lower the decapitation % to 10% if you don't want to see them.