Well, I more or less finished Ultima today. My hacking proved futile for fixing the can't-kill-enemy-ships problem, but I was able to make myself a Space Ace and finish the game. However, I later found out about a bug in Ultima that was patched some 10 years ago by a fellow in the Apple 2 newsgroup: Basically, the assembly language space combat routines use an undocumented opcode defined by the original 6502, but not the 65c02. Applying the patch, I was able to become a Space Ace! But I was unable to land again--Because I get a "program too big" error that only seems to occur after I become a Space Ace. The joy of BASIC.
I will hereby never again complain about the bugginess of later Ultima games! So I finished all aspects of the game, just...not precisely sequentially ;-)
The last part of the game only took a few minutes. You enter Mondain's "chamber," which is a big box with cute multicoliored flashes all around (much better on the Apple II than elsewhere, due to the nice rainbow pattern), where he is chanting mysteriously. Then you walk up to him and shoot him with the phazor, over and over again, and eventually the guy turns into a bat. Shoot him yet more times, and he collapses on the ground...he gets back up a seemingly random number of times before finally expiring for good, and I am told to again report my deed to California Pacific.
So, why exactly did Mondain deserve to die? I wandered around the continents, and besides the assorted monsters, the only evil I took note of was the imprisonment of the princesses in the castle! How can we explain this? I hypothesize that the princesses were a cabal who stole the time machine from its original creator to sell on the black market, and they tell you where they hid it as thanks for freeing them. So you free a criminal for the greater good!
Alternatively, the kings are just despots, but British and Shamino reform later on. The third alternative is that I'm reading way too much into a simple game ;-) But I enjoy how the game tries to retrospectively deal with some of the weirdness of the early games. Serpent Isle, for example, deals with the fate of one of the vanished continents, and I am especially fond of the way they worked in aspects of the original game (for example, the "Sleeping Bull Inn" in Serpent Isle is on the spot that the town of "Bulldozer" was in Ultima). It weaves a plausible outcome from an originally silly premise. Thee next game I'll be playing, Ultima II. has some bigger problems in terms of continuity, since it takes place on an Earth totally unlike real Earth. Most of the later games don't really acknowledge that this was true, but I guess it makes sense--only a handful of the population would known anything but Minax's torment of their realm.
Overall, it took about 5 hours to finish Ultima, not counting time spent hacking--I think the remake is a better bet for most people--but I think an upgrade to the original game using Windows would not be very hard to do, since it originates in fairly simple to follow BASIC code, but retaining all the gameplay features, plot points and graphics while fixing the bugs.