The only amount of companions i would concider enough would be 3 per class ...
One evil, one good, and one something in between ... for each class.
Or at least two per class ... just good and evil one ...
OR as bare minimum ... one per class ... it would still suck tho to loose your only Warlock, just bcs you decided to do something. :-/
And at least one per class of them should also be Origin ...
I mean come on, what is the point of having pre-defined characters to play, if you can only play some classes? :-/
Personaly i see no reason to repeat races for companions, but it seems like Larian likes Humans (Gale, Wyll, Minsc) and Half-Elves (Jaheira, Shadowheart) over Gnomes (Gale could have ben gnome), Halflings (i still hope for Helya), Dwarves (i still hope we get option to recruit Nettie), etc.
That makes me little sad honestly. :-/
It really made me sad that we didnt get any option to test mercenaries ...
On the other hand im looking forward to how they will be handled ...
And i especialy hope that lots (actually almost any) character from Groove would be recruitable as mercenary, under certain conditions.
My hopes are really high for Aradin, Nettie, Redeemed Kagha, that Tiefling Bard i dont remember the name, and Lakrissa!
Also, i really hope Goblin camp get either same, or simmilar threatment ...
I would really like to have some Hobgoblin mercenary, since they seem to be able to dress different armours.

Goblins, i dont have my hopes too high, since their models are tied to their armors.

But it would be cool!
I admit that i would really like to have all 3 leaders in my party ... Gut, Ragzlin and Minthara. :3
I would also like to repeat that if we are supposed to loose certain companions for the choices we made (aka attack/defend the grove) ... and if we indeed are supposed to get some other companions in return ... i would really like it if they would fit simmilar roles. :-/
Before Mintara was turned into Paladin, it seemed like we lost a Warlock and posibly Wizard ... to gain another Cleric ... Paladin is little better in this case, since its at least class we dont have, but it cant fill role of either Wizard, nor Warlock. :-/