Bold added by me for emphasis. Retooling old content may be a problem for you but it's certainly not the only problem you appear to have with the idea. People don't call things 'insignificant' lightly, nor do they toss about terms like 'if you must' if their position on a matter is neutral.
Besides, retooling old content - heaps of old content, not just adding in SGRAs (which would be easily one of the smaller changes if they went the herosexual route) - would certainly not be a waste. There's no denying the fact that the game was rushed and there are heaps of things that could stand improving. There could be more open PvP areas, companion quests, there could be free-control space missions, group space missions, more missions thrown in here and there to make levelling more enjoyable, there could be additional Advanced Class missions so levelling is a more varied experience between, say, Sith Assassin and Sith Sorcerer. They could put in chairs people can sit down on. They could include more in the way of galactic lore so people feel more immersed into the story.
Not everyone has already played the game so it certainly wouldn't be a waste for the new folk. These options and plenty more would potentially drag in more players - subscribers and no - and get SWTOR more money. And, as has been pointed out, they aren't changes that would need to all happen at once. Would new content be good? Yes. I'd have loved it if Makeb were considerably larger and more involved. But that doesn't mean the old stuff couldn't do with a work-over.
Besides, it's not taking them all that long; certainly not as long as you're implying. World of Warcraft is taking consistently longer. Burning Crusade came out three years after vanilla WoW. Wrath of the Lich King was almost two years after that, Cataclysm slightly over two years later, Mists of Pandaria almost two years later again. So if we use WoW as a model the SWTOR team is actually well ahead releasing new material (and that's not including the mini-events like the Grand Acquisitions Race and so forth). They could be doing nothing but patches and the occasional themed event until 2015, instead we've had several themed events and a digital expansion.
Yes, I personally consider the whole thing insignificant, but thats not important right now. My opinion that "retooling" old content is waste of time and resources isnt influenced by that at all. I would say the same thing about any kind of similar changing old content, even the new story aspects I would like. 1-50 story is good as it is. Lets think about new things to add, but add them to new content, because coming back to change old things would only make developing new story content slower.