Empirically speaking, this was already done substantially faster than any drug development process I can think of. The reason it was done relatively quickly was because as much work was done “at risk” as possible, supported by funding guarantees from the government. But that only gets you so far, and there just are steps in the development that need to be done sequentially, taking time. Happy to answer more specific questions.
There’s been a dangerous impression communicated by the media over the last few months that these mRNA vaccines were “designed” a year ago, and that everything since then is just testing. That’s not really how drug development works, particularly for a brand new modality like this. It’s a multi-dimensional engineering challenge with many, many decisions downstream of the mRNA sequence that need to be made: how it’s manufactured, how much dose, how the sequence will be delivered in a carrier molecule, how the vaccine will be packaged. None of that can be done too far in advance, because the FDA approval is contingent on those details, and could require changes.
My assumption is that the smallpox vaccination was first-come-first-served, and that they weren’t attempting to identify and vaccinate small, targeted subpopulations first. It’s the difference between spraying your lawn with weed killer and selectively hand-pulling weeds. It’s not surprising to me that the former is many times faster than the latter.