Sure you wont then mind an answer coming over a month later...
Many have soloed IWD1 and surely 2 as well. My attempt here

Gave up on both 1 and 2 before the end though.

If I tried again, I'd probably pick a smaller party than 6 for both of the games. Less inventory hassle, more xp.
Maybe 4 would do it. Classic Fighter/Mage/cleric/thief would be fine, as would be more creative multiclassing.

Small party and solo *is* possible, but the difficulty increases as well. Dale Tweaks (from Gibberlings 3) has some nice tweaks to help with inventory, and if you don't want to create an entire party check out IWD NPCs (at Pocket Plane Group).

And if you're interested, there's an IWD in BG2 conversion that ports the game into BG2 at Gibberlings 3. It's an advanced BETA that, as far as my playing it shows, is ready for full release.

I just beat the game last week (second time playing through Luremaster) and my party was...

Pali (human)
Fighter/Theif (dwarf)
Fighter (half-elf)
Cleric (human)
Mage 2x (1 male 1 female both elven)