Besides the typical AC boosts, remember that finishing off foes quicker also improves survivability.
1) Draconic Heritage opens up Draconic Skin, which gets you +1NAC. Not much, I know, but every bit helps.
It also opens up Draconic Breath, which would let you wear any armor you like while channeling your spell levels into AE breath weapon attacks that have no ASF penalty.
2) In addition or in the alternative, you could take Arcane Strike from CompWar, which lets you channel spell energy into strikes with your weapons...again, without ASF penalties.
Smiting Spell (PHB2) lets you simply channel the spell through a touch or weapon, much like the Spellsword ability. This should avoid ASF problems.
3) Like Draconic Breath, certain Reserve Feats give you magical attacks without ASF penalties as well.
If you were gestalting with Wizard, both Unearthed Arcana and PHB2 have alternative class features that switch out with certain class abilities...and some of those would give you attack/defense capabilities that don't have ASF penalties.
4) Still Spell will let you wear armor while casting spells, since it negates ASF penalties at the cost of shifting the spell's level up one.
In a similar vein, Dragon #354 has a list of spells that have no somatic components, so they too can be cast without ASF. That list is non-comprehensive- and it even misses a few spells in the sources it covers.
5) Suel Arcanomach, Spellsword and some other PrCls grant the ability to cast or channel spells while in armor...which could also let you benefit from the Battle Caster feat.