Two more Unfinished Business quests have revealed themselves to me; one a modification of an older quest, as was the case with Neb, the other totally new.
Unfinished Business Quest #3: Pai'na's Bargain
In vanilla Baldur's Gate II, this mad spider-loving woman attacks the player on sight. In Unfinished Business, a diplomatic party can pass her by in peace - indeed, if they're polite, Pai'na offers them a job.
Pai'na is a half-drow druid of the Hive Master kit, which means she focuses her attention on protecting insects - specifically, giant spiders. As a result, she's very upset that the government has a pair of lunkheaded exterminators running around willy-nilly killing spiders off in the sewers under the Temple District. She can't confront them directly because they have in their possession a magical weapon that is a bane to her beloved arachnids. So, she charges the player to go and retrieve their "evil weapon", the Spider Bane, for her.
The player needs to seek out Hurg and Jaegger, who are in the western room in the Temple Sewers, Upper Level. They can choose to either fight or offer them a bribe; 50 gold pieces, 500 gold pieces, or 1000 gold pieces. Perpetually poor and dimwitted, they can't believe anyone would be carrying a thousand gold pieces around, but five hundred is more than enough to purchase Spider's Bane from them.
Unfortunately for the player who might seek to double-cross Pai'na, the two idiots have abused Spider's Bane as a basic tool, reducing the former Two-handed Sword +3 to a broken, useless piece of junk that is only good for trading to Pai'na. Giving her the broken Spider's Bane prompts her to reward the party with 15000 EXP and the loot received for killing her; Kitthix, the Black Spider Figurine, and her Rod of Webs.
Unfinished Business Revision #2: The Hunt for Valygar Corthala
As is the case with Ungar Hilldark and Neb, an interim step has been added when seeking Valygar. To activate Valygar in his cabin in the Umar Hills, one must first confirm that he has such a place and is likely to be there. To do this, speak to his butler, then speak to either Suna Seni in the Copper Coronet, or to Llarsh the Taxman in the Government District.