They could follow what Mass effect does and have you either start new or load up the choices you do in mass effect 1 will effect what happens to mass effect 2 and what happens in ME2 will effect ME3
Right, but they still have to
program all the results of those choices. That's my point. The amount of crap they'd have to make, to allow for all (heck, even just the major) choices' results to be shown in a "continue" DLC would be as much programming as the entire original game.
It's just not feasible.
And for the "But I don't care about the epilogue" guy - ok, so why do you even have to finish the MQ and get the epilogue then? Just wander off into the wastes and explore instead of going to The End.
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Really don't understand the problem. The vast majority of games have an "End". And that's been fine for decades.
FO3, I knew there was an "end", so I did a bunch of sidequests, explored, and then finally finished the MQ at ~25 hours to see the finale. Then said "Ok, that was kind of silly", reloaded my save and explored for another 50+ hours. It was fine. (And in the year+ since then, I've played five more characters. Four of them ignored the MQ completely. The fifth did the Broken Steel version of the MQ.... and I then promptly removed BS from my install because it screwed up the game with it's continuation, level cap increase, and annoying new monsters.)
FO:NV, I knew there was an "end", so I did a bunch of sidequests and exploring. Finally got into the endgame at ~40-50 hours. Saw the finale through, thought it was depressing as hell, realized that there were a billion other ways I could have gone though the quests to get a different result, and started making a new character to try again. (Also, I realized that FO:NV is so focussed on plot that it has barely a fraction of the "explore" potential that FO3 has, and there wasn't much point in reloading my old save again. FO:NV's replayability is in the massive number of ways to go through it.)