Hi, I joined to give some feedback on this. I've backed for the time being but I really think you should listen to the backers about the bases. Almost every single comment is about the bases which should tell you something.
I understand that you want to make your own unique game out of this and that the bases are an integral part of that. Unfortunately most people will be looking to expand their 6mm collections for other games. While plastic bases are very nice to have, more minis are better. Bases can be MDF add-ons, or rendera plastics easily enough (as others have pointed out). You don't even really need the dimples in them, the individual model bases aren't that noticeable when sand and flock has been glued on. The bases are taking up a ridiculous amount of sprue space which could be used to almost double the amount of infantry, or add another vehicle or two to the sprue.
Let's give an example. Mantic makes alternative plastic miniatures that can easily be used for Warhammer Fantasy. Their game, Kings of War, uses fixed unit bases rather than individually based models so all the models of a unit fit onto one base. Do you think they would make as many sales if they devoted half of their sprue space to a base for their style of basing? I bet that most people would not want to buy Mantic minis because they're getting the minis for the minis, not for the bases. Not only are you wasting sprue space on something that can be sourced elsewhere but you're also devoting it to one style of basing that's not to everyones cup of team. I bet most of your potential customers don't actually want round bases, they want E:A style bases.
By all means have a separate base sprue as one of the first stretch goals (a very logical first stretch goal) but please devote as much of the initial sprue space to minis and vehicles as possible.
Also note that Renedra do round plastic bases that would be suitable (albeit without dimples) and are often used by other manufacturers for basing (almost all plastic historical boxes use Renedra bases):
http://www.renedra.co.uk/webstore.html I'm sure they would be happy to allow you to have add-ons for their bases.