I like this change and am curious what type of overhead this has for the p2p network. Do the p2p improvements you mention cover this additional overhead?

There has been talks of speeding up transaction times to allow for better interactivity for users. Potentially 2 or even 1 second block times. The general feedback it is definitely possible at least in theory. Would 2 or even 3 second block time be possible with this additional overhead?

Like I mentioned in another comment, it is my experience most dapps use HEAD so they accept the risk (knowingly or not) of reversible blocks in favor of speed. Exchanges I believe are the main ones using IRREVERSIBLE. For most dapps they would see near similar speeds as HEAD but the protection of IRREVERSIBLE, which is a great best of both worlds scenario.