Ok, first: no there's not a way I know to put hideous blast on a full attack, but there are a few interesting things about it (see below).
My build is:
Warlock 20//Paladin of Tyranny 5/Warblade 5/Kensai 10
Warlock is a pretty solid class on its own, but Paladin isn't really recommandable over level 5 (you'll start at level 4/4 to avoid multiclassing penalties).
Pluses: difficult to reach, good damage output.
Minuses: being far from melee means you'll need another tank and you'll never really use your aura. Also, you cannot fly in medium or heavy armors. That means one less feat, but also 4 less armor points and no heavy black armored flavour
Now: Warlock side isn't particulary difficult to make out, just one thing: use the PHBII version, you don't need fiendish resilience, better out with fiendish flamewreath.
INVOCATIONS:
Least - hideous blow, entropic interdiction, see the unseen
Lesser - fell flight, charme/walk unseen (both good, but not that good in a fight)
Later on:
Lesser - Relentless dispelling
Greater - Wall of Perilious flames, Freezing Tentacles, Vitriolic blast
Dark - Dark prevision, Caster's Lament and Darkness Scorporation
Paldin's side: first, take two Paladin alternate class features: the first being Unholy Warrior (Complete Champion) that grants you a bonus feat instead of spellcasting; the second being the Charging smite (since you fly you don't need a mount) that will be good with some flying feats.
Second, since you want to be a party player I thought some White Raven manoeuvres couldn't hurt.
Third, kensai is a good class and since you are lawful anyway it adds a little bit of theme to the character. However, you are going to get a +10 weapon for free and some good class features (I know your DM said that you cannot make your own items, but this isn't crafting, it's more like a class feature) and it will let you get a lance as you want it, with the right properties (valorous, charging etc.)
MANOEUVRES AND STANCES:
Action Before Thought, Battle Leader's Charge, Wall of Blades, White Raven Tactics, Emerald Razor (and on next level Ruby Nightmere Blade).
Leading the Charge, Absolute Steel Stance.
FEATS:
You have, being human, 4 feats + 1 Paladin feat. Ask if you can use Flaws (Unearthed Arcana, page 91; if you do, take Shaky [you'll use mainly hideous blow, and when you don't, you'll get a touch attack] and Weak Reflexes [Action before Thought is there for it] and in exchange take Improved Bull Rush and Power Attack)
Take at level 1 Weapon Focus (knight's lance), and Combat Expertise
At level 3 take Flyby Attack
At level 6 Diving Charge
Paladin 4 take Divine Might (Cha on damage, swift action, burn turn attempt)
This is based on the fact that Flyby Attack allows you to use a standard action, not a simple attack. This means both manoeuvres and hideous blast.
Add a bit of an Uber Charger and you'll have a big damage dealing flying character that is always too far for a full attack. Add that you