Thought the first: corned beef and cabbage is, in my opinion, disgusting. A day on which you're not allowed to eat corned beef and cabbage sounds like a fine idea to me.
Thought the second: Allowing people to eat meat on St. Patrick's Day when it happens to fall on a Friday during Lent seems to me to be akin to canceling your worship service when Christmas happens to fall on a Sunday. The whole point of Lent is to recognize Jesus Christ's 40-day fast in the wilderness by undertaking a symbolic fast of your own. That's what Mardi Gras is all about: it's your last chance to whoop it up before the forty days of fasting and sorrowful reflection. If there's one time during the liturgical year during which Roman Catholics should not under any circumstance eat meat, it's Lent. One might therefore argue that this special St. Patrick's Day dispensation is borderline blasphemous.
Thought the third: On the other hand, Roman Catholics routinely eat fish on Fridays, even during Lent, and the last time I looked, fish is meat. So maybe it's not that big a deal after all, since most people don't seem to take it very seriously in the first place.