I want them all, and depending on the sculpt quality and the state of my finances, I intend to buy them all. I also have my own personal favourites that I would of course like to see sooner rather than later.
However, when choosing what to make in which order I think other factors should come first. Things such as keeping in mind that some of the older Doctors are already getting up there in years (so a signature edition, if planned, would be wisest sooner, rather than later), and also spreading things out to take advantage of current trends and popularity (so making sure to keep the NuWho fans attention, while also capitalising on things like the renewed interest in Troughton thanks to recovered episodes).
So with all that in mind, after Hartnell I'd probably go something like this:
The War Doctor or Night of the Doctor based Eighth Doctor - scratching that 50th anniversary, current series itch. Plus, if they are going to do The War Doctor at all, now would probably be the best time.
Second Doctor - while the recovered episodes flame is still burning brightly, and interest in early episodes is still running high.
Capaldi's (Twelfth?) Doctor - Going to want to get this out as soon as possible after his on-screen 'look' is confirmed and fans have had a taste of his personality on screen.
Sixth Doctor - Colin Baker's not getting any younger, and love it or hate it, that outfit should look great on a figure.
Ninth Doctor - Somehow I don't see a signature edition for this one, no matter when it is made. Stranger things have happened, though...just not many.
Seventh Doctor - Sylvester McCoy's not getting any younger either.
Eighth Doctor - only if the War Doctor was made above, otherwise already been done, so disregard. Either way still think that the Night of the Doctor version will probably sell better, especially as that minisode seemed to be a hit with both old fans and new.
Third Doctor - But will he have Venusian Kung-Fu grip?
Fifth Doctor - Only so far down the list because he's eight years younger than both Colin and Sylvester, so should be around for a good while yet (of course, here's hoping they all are).
After that they can consider getting a bit more 'specialty market' perhaps, with the likes of a Hurndall First Doctor variant, doing The War Doctor if they didn't make him already, maybe even a Peter Cushing movie version of 'Doctor Who' if the rights are cheap enough, as well as revisiting the most popular, already released, Doctors in notable variants (smiling Tom Baker in one of his later outfits, Tennant in the blue suit, TV movie McGann - assuming they did the Night of the Doctor version first, and so on...).
Hell, it's what I'd do anyway. But what do I know?