Even though the original owner put some extra "wood" on the dash and some really nice painted pinstripes down each side (I don't think they were original), I'm still a bit of a purest. Most of what I would change would be simple things like adding a windscreen which I just haven't bothered to do.
One of my bigger wishes which would "improve life" would be a better HVAC system so I don't have to keep fussing with a system that either doesn't blow adequate heat on cooler days or cold on warmer days. There was some sort of a "conversion" done prior to purchase from the original owner, I've had the system charged which lasted one season, had the mono-valve changed at another time which lasted one or two seasons, but it's still virtually useless most of the time. Thankfully, I only drive it about 1,000 miles a year!
Other than that, the only thing I might do is change it to an Austin Healey 3000 Mark III. I had the British version of PIA cars back in the 60s/70s, but never had a Healey!