For me:
>> 1) have you purchased any Battleforce scaled Minis yet, either in the packs or in the singles
Yes - three copies of each pack (IS and Clan).
>> 2) do you plan on purchasing them?
Yes - individually from now on (a.k.a. see above :) ).
>> 3) limit four designs if you could add to the line what would you add?
Four is rather restrictive, but I'll try. For both I'd want widely-used, older designs - suitable for use in several eras of play. So...
Inner Sphere: Archer, Warhammer, Phoenix Hawk, Awesome.
Clan: Mad Dog (Vulture), Stormcrow (Ryoken), Summoner (Thor), Executioner (Gladiator).
NB: The Warhammer edged out the Marauder only because I prefer the former's Re-Seen look.
Several posters in this thread have decided not to get these things because of their investment in the regular-scale minis. While I can accept that argument, I have no problem with using either scale for both Total Warfare and BattleForce games. Smaller figures allow proportionately larger play areas (as scatcat said) and ordinary-scale Mechs work just as well to represent a BF lance (as several people said).
I can think of a few more uses rather than *just* BF games, namely:
(1) Test dummies. Some paint schemes are easily imagined while others are hard to get "just right", especially if you plan to paint an ordinary-scale company in those colors ;) . Better to wreck a $5.00 figure than a $15.00 one.
(2) Fog of War. I know I'm going to have a few lances/stars of identical Mini Mechs in matching paint schemes - they'll make much prettier "dummy counters" for simulating hidden movement or double-blind play without needing three identical terrain boards.
(3) ProtoMech proxies. Again a matter of personal taste, but I hate the "monstrous" look of the original Protos (although the new ones from Wars of Reaving/TRO: Prototypes are much better). I can also use BA minis to proxy as Protos for the Mini Mechs at BF scale.
(4) Solaris VII duels. Aside from two Mini Mechs plausibly being able to occupy the same hex (or at least poke their feet into the same hex), the smaller scale lets me run two or four duels on a single 6'x4' terrain board. This should help if my gaming venue gets crowded with other games or if I have trouble getting enough battles played to run a plausible Solaris league campaign (always a long shot, but I can dream, right? ;) ).