Launching AT rockets w/o AT launch controller

I'm getting back into rocketry after many years ago launching a bunch
of littlish rockets. I've been launching some Estes kits and rockets
built from Estes parts in on D's, and want to get into the mid powered
E/F/G range. I'm checking out the kits from Aerotech and really like
what I see.
Anyway, I'm on a bit of a budget (I've got another rather expensive
hobby already) and am going over what I've going to need. Right now,
I've got a suitable launch pad, I know what I'm going to have to get
in the motor department. However, I'm rather hesitant to drop about
$50US on AT's "official" launch controller. I've a standard Estes 6V
one, however.
Now perhaps I'm just undereducated in the workings of model rocket
engine ignition, but it seems easy enough to make an external battery
pack to deliver the 12V potential through my Estes controller. Perhaps
this I might break the controller's light bulb by doing this, but
outside of that, this seems to me like it should work.
Am I completely (or partially) wrong in this conjecture? Is there a
special characteristic that the "official" 12V launcher might have
that could not be reproduced using a modified Estes 6V controller? Or,
am I better off just putting another shift in and plopping the cash
down for the "real" controller?
Thanks for any input.