The prequel battle droids not looking like IG-88 was a missed opportunity.
Well, the first Clone Wars TV series did have these guys; http://starwars.wikia.com/wiki/IG_lancer_combat_droid
(Having read through the wookieepedia articles for the IG series it seems that the EU guys agree with you. A lot of PT droids were retconned as being IG droids.)