Neonchameleon
Legend
Warlord I think could work under the fighter banner - starting with a couple of warlord-y fighting styles to make the warlord meaningfully worse at combat than a fighter as they spend the resources on support. And bringing warlord into fighter would help deal with higher level emptiness.i feel like it would be just as easy to dig up one of the many old threads that discuss that very topic and have over half the work already done for us.
but personally i think the major missing positions are
warlord
swordmage
psion
shapeshifter/monster class
summoner/pet class
Swordmage I think could be briught in under the aegis of a bladelock. Mixing magic and melee - then you have some sort of mark-equivalent invocation or spell.
Psion is already there as Aberrant Mind Sorcerer. To get more you need psionic powers to be entirely different from spells, and dozens of pages of them (the 3.5 psion had 70 pages). And I don't think they are going to do that.
Shapeshifter, agreed. Probably a build-your-own martial class?
Summoner - again agreed.