It's a shame it's too late to make class suggestions as this character's ripe for factotum (Du 14-20). More levels of wizard would really be a boon, too. She's already a wizard, so she's a conjuration specialist who took the alternative class feature abrupt jaunt (PH2 70), right? And since you don't care about her being especially effective, taking Mnk1 and beating up a sparring dummy of the master (AE 137) (30,000 gp; 40 lbs.) to get that 10 ft. of movement required for to use skirmish is kind of a thing. Anyway.
Obscure Feats
- The uncategorized feat Hardened Criminal (City of Stormreach 95) grants the creature immunity to attempts to Intimidate it and the ability to take 10 on 1 skill picked when the feat's picked. Note: This feat sprang to mind immediately when you mentioned your character's focus on the Escape Artist skill.
- The fighter, general, and Chult and wild dwarf regional feat Disentangler (Rac 162) grants the creature a +2 bonus to Escape Artist skill checks and a +2 bonus to opposed grapple checks.
- The general feat Daredevil Athlete (CS 76) as an immediate action 3/day grants the creature a +5 competence bonus to a single Balance, Climb, Escape Artist, Jump, Ride, Swim, or Tumble check. I assume the intent is the next one, though. As a competence bonus, it'll stack with the circumstance bonus from masterwork tools but not the competence bonus that often comes from magic items, which is sad.
The aberrant feat Mourning Mutate (Dragon #359 110) as one of its benefits grants the creature a +3 racial bonus to Escape Artist skill checks from being "unusually flexible." It's 1st-level only and can make the creature look scary, awesome, or scary awesome at the DM's discretion. As it counts as the feat Aberration Blood (LoM 178) (which could instead grant the creature +4 racial bonus to Escape Artist skill checks, but the creature then has "slimy skin"--ew), it grants access to...
- The aberrant feat Inhuman Vision (LoM 180) grants the creature darkvision 5 ft. per aberrant feat and a +1 bonus to Spot skill checks per aberrant feat.
- The aberrant feat Scavenging Gullet (LoM 181) grants the creature a +4 racial bonus versus ingested poisons and diseases. More importantly, it grants the creature the ability to "gain nourishment from eating any organic material, despite its freshness or source." For a sensate, this is gold.
- The fighter and general feat Master of Mockery (Dragon #333 88) grants the creature the ability to make a Perform (comedy) skill check as a standard action. The check's target makes a Will saving throw (DC = the Perform (comedy) skill check's result). If the target fails, it's enraged, gaining a +2 bonus to attack rolls versus the creature, taking a -2 penalty to Armor Class, and attaking the creature "whenever able." Talk to the DM about the effect's duration.
- The tactical feat Combat Panache (PH2 93-4) grants the creature use of 3 tactical maneuvers that are wildly subpar or difficult to use but a a lot of fun. Two maneuvers actually require the creature to be hit and take damage before they can be used, and the other requires the creature to hit and inflict damage before it can be used. Nonetheless, they're flashy and fun.
For basics, Beguiler 1/Wizard 4/Ultimate Magus 10 (or however far you get) is by-far the best choice. Beguiler 2/Wizard 3 as entry is not going to get you killed or anything, but it is a dramatic loss of power relative to only a single lost wizard level.
Cloaked Casting
From an optimization perspective, Cloaked Casting isn’t nearly worth what you lose in terms of wizard spellcasting.
Unfortunately, Cloaked Casting is rather minor in general. There’s no reason you can’t surprise your opponents with your spells, and just not get the +1 DC bonus. Surprising people is usually a pretty good idea anyway (though feinting in combat is not). You will be better off doing things this way.
But feel free if you really want Cloaked Casting to get it. Just be aware that it will cost you more than it ought to.
You don’t have to ban Illusion if you don’t want to
Wizards get illusions that beguilers don’t, and your wizard spellcasting will be superior to your beguiler spellcasting. If illusions are important to you, keep it on your wizard; having it on both classes will really play up its importance to your character.
So illusion could be very valuable to you; don’t ban it just because you think it will be redundant. It won’t be if you use it right.
You really don’t need area-damage
Conjuration and illusion are excellent at battlefield control, which means rather than simply damaging people in areas, you’re hitting people in areas with nastier effects, and stuff that warriors cannot do. Damage is easy, and lots of classes do it as well, if not better, than spellcasters. In a lot of cases, though, that’s all they can do. So let them do it.
And ban evocation.
Metamagic
Go for it! Ultimate magus gives you powerful abilities that allow you to use your second class to power metamagic for the first, which works very well. Definitely a good choice.
Shadow Spells
Ideally, you do not want to use shadow evocation or shadow conjuration offensively, because you give the enemy two chances to save, which is bad. As such, I don’t really suggest relying on them for that; they’re massively better as buffs or what have you. Spell Focus (Illusion) is still a solid idea though.
Best Answer
I recommend a few Blessed Bandages (Magic Item Compendium, page 152). Applying one immediately stabilizes a dying target.
As for your proposed solutions: