I am a strong proponent of leaving Ascension Thursday on a Thursday. I think it is more important as a feast than some existing holy days of obligation, so if we are going to have holy days of obligation, the Ascension should be one of them and something else should be dropped. I started a similar thread in the Liberal Catholic sub-forum a week or two ago here on CF. Thanks for bringing it up here on the main forum.
Although, I will say in general that I don't like the idea of having feasts that must be attended on pain of sin. Rather, I think we should change of holy days of obligation in general to mandatory parish mass days, where two masses must be celebrated at minimum, once in the morning and once in the evening, to give people a chance to attend important feast days on their calendar days, and where they are highlighted on the calendar, without any sort of threat of it being considered a sin if you don't want to go. Same with Sunday masses.
I love the idea of feast days and particularly important feast days where there are more ornate and better attended masses at better times instead of just a quick daily mass absurdly early in the morning, without the concept of obligation.
A lot of people go to Ash Wednesday masses and it's not an obligation.
I'm digressing a bit, though. *If* they are doing Holy Days of Obligation, this should be one, and it should be on a Thursday, as it is more venerable and important than some existing days of obligation in the US.