Here, even if the new characters were done really really well, they'd still break the game. A great deal of the strategic fun in BG2 was compiling your party. You'd have a number of elite NPCs - the paladin, the evil fighter, Viconia and Yoshimo. Most of those either create extra enemies in some areas, or (much more importantly) have direct clashes with other party members, limiting the number of elite NPCs you can take
While I enjoy BG2 a great deal, I think you're overselling the impact here.
Generally, the only conflicts stem from Evil characters, and the only "high-tier" Evil character is Edwin, who clashes with Aerie and Keldorn.
Korgan is, arguably, the worst NPC in the game. Sure, he has decent stats, but he doesn't really have anything else. Five pips in axes is rather worthless seeing as the best axe(s) in the game (not including ToB) happens to be +3 with a couple points of elemental damage tacked on. His evil alignment also prevents him from using the outstanding undead-slaying, throwing axe...which is a real disappointment (and slightly ironic considering his personal quest revolves around raiding some catacombs full of undead). Other straight warriors offer a lot more. Minsc and Valygar both come with much more relevant proficiencies in addition to their Ranger spellcasting abilities...to say nothing of the fact that Minsc can replicate Korgan's bersking and Valygar can backstab as well as cast pertinent mage spells. Korgan stacks up terribly against Keldorn, who not only has outstanding anti-mage abilities, but can also wield some fearsome weaponry, be it his default blade or the Carsomyr. Basically, Korgan is on the same level as Mazzy...except Mazzy has decent proficiencies slotted in as well as personal equipment and good special abilities (Haste).
Viconia looks good on paper; that 18 Wisdom would be a necessity for any high level Cleric endeavors in a by-the-book 2nd Edition game. But BG2 frequently skirts the rules and even Anomen, with his foolhardy 12 Wisdom, can call upon the might of 7t level Cleric spells. So because of this, Viconia doesn't bring much to the table. Certain stats relevant to combat, like Strength and Consitution, are subpar in as much to bar her from playing double duty; she's mostly relegated to behind-the-lines spellcasting duty. Other Divine casters don't share this frailty. Jaheira and Anomen are both Fighters, Cernd can shapeshift into a (greater) werewolf, and even Aerie can be geared to combat effectiveness with the right Mage spells. Viconia can't really do this, and all she receives in return are a few extra casts in the lower levels of Clericc spells...not much to write home about.
The only real character of note out of the three Evil NPCs in Shadows of Amn is Edwin, and mostly because he has hax that grant him additional casting slots per spell level beyond what a typical specialist mage can achieve. Basically he forces a choice between his services and those of Aerie and/or Keldorn; given that those three are, in my opinion, the best NPCs in the game, it actually becomes an interesting choice.
Bioware's experiment in making the Evil-cru a bunch of high prime-requisite(s), "pure" classes didn't work out too well, and since the only conflicts were between Evil characters and certain Good ones, a lot of the strategic complexity was diminished. It would have been nice if Korgan and Viconia had been granted buffs equivalent to Edwin's bonus spell slots or if inter-party conflict/friendship had gone beyond simple alignment polarity disagreements. Imagine Valygar getting upset with Nalia because she is a noble mage...someone who Valygar doesn't quite trust nor like. Or Viconia "corrupting" Aerie, and turning her against other party member in favor of some female (elf) supremacy-cru.
Essentially, party conflict was an interesting feature in BG2...but I feel it could have been so much more than it was.
But in BG2 as is, one of the big strategic improvements upon BG1
A similar mechanic was actually present in BG1. A lot of party members would become uncontrollable and fight with one another if they were kept in the company of one another for too long. The most notable example is Xzar/Montaron and Khalid/Jaheira or Edwin and Minsc/Dynaheir, but I'm pretty sure I recall Kivan not getting along with Viconia and Shar-Teel and Yeslick coming to blows with Kagain. There may have been others too.
It was only a challenge for the challenged. Practically any assortment of characters can pretty much shit on 95% of the content in Baldur's Gate, since it all comes to the cheese. It doesn't matter which thief you carry with you. It doesn't matter which fighters you carry with you. As long as you have a mage (no matter who) and somebody able to carry a couple of the broken items that make the areas that had any sort of intrinsic difficulty just a chore (mace of disruption, Shield of Balduran...). You can steal a fucking ring that makes healing spells useless as soon as you leave the first dungeon. You get so much gold and crap during the game, that you could quaff a couple of "immune to the next encounter" potions each time you have to fight and still have more money left than you can ever use during the game.
The BG series might be many things. Challenging isn't one of them.
Basically what you're saying is that the difficulty of an RPG with no reflexive and few random components becomes trivialized when the player has a strong knowledge of the systems and content within the game?
Shocking.
