Who do you choose?
And don't say Pikachu!!!
:)

Pikachu!
I import my character from the original game and mostly I choose for the rest team, Shadow, Raider, Igor and/ or Danny. Sometimes I choose Fidel to come with me or Ivan. But Ivan not very often. I hired him in JA1 the most time, but in JA2 not because there are other good mercs, imo. :)

La Malice is all I care about. I live in Ottawa so I find him particularly entertaining.

I'm amazed that you can import - there is a bug with importing characters in v1.00 which is what GOG offers. It's fixed in v1.01 but that's little help... Still it supposedly works for some - so good for you :)
As for starting team. First of all my favorite mercs are Igor, Barry, Ivan, Shadow and any one of the doctors, but starting out I'll go for Igor and Barry (both great value for the price) and then a strong high level merc as well - depending on the difficulty which changes starting $$$ and thus who you can afford.

Ivan was a good one to go with for starting out in JA1. For JA2, he was always out of my starting price range. Grunty was another good pick as far as shooting in both games. Fox for first aid. In JA1, I tended to mix things up as far as other slots, mainly what I could afford after Ivan and Grunty. In JA2, pretty much the same thing, though Barry and Shadow were among my top picks, especially if Grunty was unavailable.

Steriod for the mechanics and early lock pickings. What he can't pick he can use a crowbar on with his strenght. Later on in the game I use Magic for lock picking. Steriod has markmanship in the 80s at the start.
Fidel for the explosives. He also has a good markmanship to start with. He was also always 1 of my mercs in the first Jagged Alliance.
Burns for her medic skill and markmanship.
My IMP merc normally has markmanship at 85. Mechanical, medical, explosives at 0. Wisdom high, leadership at 35 and the rest divided over health, strength, agibility and dexterity. Hope I didn't leave anything out.
For me this is a good starting thing with the basics covered.
Ira joins the team off course and I normally use her for her medic skills and leadership capabilities. Due to her wisdom she learns quickly.

IMP (60 HP, 70 STR, 85 DEX/AGI, 85 WIS, 35 LDSHP, 35 MECH, 0 EXP/MED), Igor and Grunty to begin.
Wolf to follow shortly, along with Trevor, Spider, Raven, and Dr. Q as the game and my needs progress. (I run a heavy night-ops team, can't stand daylight encounters. Plenty of mechs, Grunty handles the heavy weapons and plenty of accurate shooters. Spider and Doc Q are there for the heavy medical work, everyone else has bare minimum for patch jobs.)
MERCs used for militia/mule work, other AIM mercenaries hired on as required.

I start with my IMP Merc named BigDaddy Game settings are Expert, Tons of Guns, Iron Man.
I go in alone then get Ira and wait a few days and get Razor. I then train then until I receive the last bad E-mail from U know who then start taking over Chitzena. Then I head to the airport and on my way I hire Bull. For those of you who have never used Razor he is a Rambo once you get him to lvl 5 or higher he is a real killing machine. Bull I love the way he can take a pounding and still chug on all the while yelling "Come on you sons of bitches is that the best you can do" I cant start a game without getting Bull he is my favorite hard azz. Then after I take the airport I take the rest of Drassen then run back and get Dimitri AKA Dummytree lol. Then I run up and get Maddog & that is my Squad that I win the game with. My starting squad. I love to train these guys into killing machines. It takes awhile but a lot of fun when your done.

I normally play 1.13 on INSANE and rarely play vanilla JA2 now.
Seeing as 1.13 gives you 6 IMP's they are usually:
Lenriak - Throwing and Auto weapons (psycho)
Punisher - Heavy weapons Specialist
Spanner - Explosives/Engineering Specialist
Vixen - Sniper
Helios - Auto weapons Specialist (and a psycho too)
Karebear - Medic
AIM Mercs that I commonly hire are:
Shadow, Ivan, Igor, Buzz, Raider and Raven
Sometimes I consider using the following instead:
Red (just because I'm scottish), Spider, Trevor, Barry and Fox
I never hired from MERC.
My Vanilla team was:
Lenriak (Auto weapons Psycho - And a Friendly Psycho too), Barry, Fox, Ivan and Bull. With some of my previously mentioned mercs added as needed.