The feat you need is called Shorten Grip, from Dragon Compendium.
http://realmshelps.dandello.net/cgi-...orten_Grip,DC1
It allows you to threaten/attack adjacent squares with a -2 penalty. It does not require an action.
Do you have a race yet? See if your DM will allow Hengeyokai from Oriental Adventures. Transform into a sparrow (fine size, +6 Dex bonus, +8 Size bonus to AC, +8 size bonus to attacks). A sparrow with Eldritch Glaive, Shorten Grip, and Confound the Big Folk would be... interesting. It might also get a few books thrown at you.
Oh, something else you may want to explore with a Warlock... pick up a Wild Cohort as a mount. Eldritch Glaive can be used while mounted to get the equivalent of a full attack, even if your mount moves more than 5'. (Although with all-day flight, it's not like warlocks have movement issues.)