I have an 81 and I have found that the best upgrades to the boat by far have been to glue my pylons and have the hiking straps re-sewn. As far as the Aussie rigging thing goes, if you are sailing solo, you probably won't get to a point were reefing your mast back any further than standard equipment will let you will make any sense at all. I have sailed mine with the standard rigging thus far and have been able to rake the mast back pretty far without new stays.
Ditch the Coors bottle caps and cup plastic practice golfballs in half. There half the price and work great. Helps the mast rotate without all the cap grinding.
Other than that, sail the boat AS IS and when something starts to bug you, change it. I could give you 20 things to change and they wouldn't work for you at all and then all you have is a boat you can't sail. The Hobie 16 is a great boat the way it was made and until you have sailed it extensively, you won't know what changes YOU want to make anyway. Just sail and enjoy.