I decided to go back and look at what figures I had (or didn't have, as the case may be) that were both rare enough/demanded enough to be reissued AND were sculpted to the standards of today's figures (when they're being done well, I mean). Not surprisingly, the list was pretty short:
-Everything in POTF2 was disallowed. None of that stuff holds up today, period.
-From Episode I, the only figures that I could honestly say held up well and are extremely difficult to find were the Pit Droids. And by "Pit Droids", I mean the ones released in the foreign two-packs which weren't released in America. And by that I mean the ones that I'm too cheap to pay for on the secondary market.

-From POTJ, nothing really stuck out as being rare to me. The only truly rare piece from the POTJ days was the MOTDS two pack, and both figures from that have been rereleased to the point of redundancy, and have also been subsequently surpassed in quality, sculpt- and articulation-wise. Sorry POTJ, you're SOL.
-Saga 2002: Ephant Mon. That's it. Everything else pretty much sucked.
-Saga 2003: McQuarrie Stormtrooper, and we're getting that anyway.
-Clone Wars 2003: SUPER ARTICULATED CLONE TROOPER...enough said.
-Saga 2004: Again, absolutely nothing. Okay, maybe the TIE Fighter Pilot if they don't intend on doing a Vintage line version.
-OTC 2004: AHAHAHAHAHAHAHA! We're voting on repacks from a line of repacks? Oh Hasbro, what won't you resort to?
-VOTC 2004: Stormtroopers, Stormtroopers, Stormtroopers, and more Stormtroopers.
-Post-OTC 2005: Maybe the three Cantina guys, since people had trouble finding them in some areas and they *are* nice figures.
-ROTS: Threepio. I can't find him anywhere.

-ROTS (seriously): A correctly painted Commander Bly. Other than that, they've reissued the line to death at this point.
-Saga 2006: Who's popular enough and hard to find enough to warrant being rereleased so soon? Scorch? Is that about it this year? I'm sure we can do a precognitive thing and put Commander Appo on the list just to be safe, but out of all the 2006 figures, it seems like Scorch is the only one not seen on a fairly regular basis at retail, even after months of being released.
-VTSC 2006: Biker Scout. Duh.
So going by that list, here's the assortment that would work, IMO:
2 x 2003 Clone Wars SA Clone Trooper
2 x 2006 VTSC Biker Scout
3 x 2000 Episode I Foreign Pit Droids (three in each bubble, three colors)
3 x 2004 VOTC Stormtrooper
1 x 2005 ROTS Correctly Painted Commander Bly
1 x 2002 Saga Ephant Mon
Or, since Bly's probably already coming, crank that Stormtrooper up to 4 per case. Seriously.