Really, why bother with precision based damage anyways? You've got much more potent options available to you than merely doing damage. That's what the meat shield is for. A Beguiler is better off locking down critters than trying to blow them up.
However, if you truely wish to be able to blow things up, may I make some simple suggestions?
1) precision damage is made of fail. It doesn't work on many things, it's difficult to get to work, and in general is sub-par compared to area effect stuff.
2) Spontanious Summoner feat (Complete Divine) lets you summon nature's ally. Basically, adds all the SNA spells to your list of spells known. Handy, eh? This can be used to threaten opponent casters, set up flanking opportunities with your meat shield, cause general disruption in opponents, trigger potential traps, and with Unicorn, can also be used to heal.
3) Extra Spell feat (Complete Arcane) lets you add one spell to your list of spells known. Unlike the beguiler class ability, you can add anything, not just Illusion or Enchantment. Add in something to blast with like Disintegrate. Have fun. If you absolutely, positively demand on using reserve feats, grab Orb of Sound, and the feat Energy Subsititution to change flavor around as necessary to power various reserve feats. Generally thought of as a normally sub-par feat, but it certainly beats loosing access to Beguiler class features to do precision damage.