Formally JA Crossfire is a stand alone game, but it is a DLC to JA Back in Action. You have a new story on ten new maps.
JA Crossfire uses the same engine like JA Back in Action.
In the Guide to JA Back in Action you find basic informations about moral and combat.

http://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=179688409#198103

My Review for JA Crossfire

Supporting Skills
There are three kinds of support and for each you need a specific basic skill minimum to use the important tools:
M) Medical for healing team members
C) Mechanical for repairing weapons
E) Explosive for removing mines
You should have a merc with the medical level M3 and a merc with the mechanical level C5 in your starting team. In JA Crossfire a merc with explosiv level E2 for defusing land mines is not needed for the first maps.

Medical

Craftsman (Mechanical)

Explosiv

Possible teams with at least the abilites to use bandages(M3) and to repair red weapons(C5).
Spider is a precondition for hiring Static.

• Static and Spider, they give each other the moral bonus.
  
• Buns and Bubba, amongst the starter mercs with medic skills, Buns is the best shooter.
  
• Biff, Flo and Bubba, three mercs and two of them with moral bonus.
  
• Wolf, the one man show.

In Crossfire you have only 30,000$ to hire a starting team.
Some mercs have changed in price, level, traits, stats or gear and there are new mercs you can hire only in Crossfire.
The starting weapons from Fox (MP7) and Thor (G36C) can be useful for a quest later in the game.

Name price (level, medical, explosiv, mechanical, marksmanship):
Flo 5,285$ (L1, M2, E1, C2, 42): She is new and really cheap. She likes handguns and shotguns. Also she has a small medical talent, which benfits from her high intelligence. She likes Biff.
Gumpy 8,000$ (L1, M2, E2, C1, 36,): A new young intelligent merc with a with an explosive value of 70 and the trait Explosive Expert. With his other traits he has very good morale as long as he has full health, but his marksmanship is low.
Bubba 8,321$ (L4, -, E2, C5, 63): He can remove landmines and repair all weapons at a very low price.
Spider 10,170$ (L2, M5, -, -, 55): She is now level 2, but stats are changed only minimal. She can use all medical gear and is ready to join you at start. Don't forget that her trait Night Ops compensates only at night the bad trait Amazon. She and Static like each other.
Razor 10,850$ (L3, M1, -, -, 13): The values speak for themselves. You only can try sneak attacks with him or use him as a mule.
Red 11,680$ (L4, -, E3, C3, 58): The price is 1750$ cheaper and nothing else has changed. He is a good explosive expert, but you don't need one right from the start. He needs to find glasses, because of his trait Short Sighted.
Steroid 11,850$ (L1, M1, -, C5, 61): The hiring costs are 500$ cheaper and all stats are unchanged. He can repair all weapons and with his trait Macho it's easy for him to get the moral bonus.
Barry 12,075$ (L3, M1, E3, C4, 61): With his level up Barry improved his marksmanship, but now he is not ready to join your team directly.
Gasket 12,500 $ ( L2, -, -, C5, 43): A very good mechanic (87 dex, 82 mec).
Biff 14,710$ (L2 , M4, -, -, 62): He has the traits Handgun and Bargainer. He likes Flo.
Grizzly 15,750$ (L2, -, E1, C2, 62): He is not ready to join you directly, but who cares?
Haywire 18,150$( L2, -, E1, C1, 66): Haywire is a good shooter in combination with his very good traits Assault Rifle (Expert) and Sub Machine Gun. He hates Biff.
Cliff 18,275$ (L4, M5, E1, C2, 68): The equipment costs are reduced, because of the worse weapon.
Static 18,562$ (L4, -, E1, C5, 63): He is now cheaper, but got with Unfit a new bad trait and lost skillpoints in mechanical and marksmanship. He is totally worth his price and joins you only if Spider is already in the team.
Bull 18,700$ (L3, -, -, M2, 58): The trait Unfit is now replaced by Machine Guns and some stats are improved. Without the price doubling you could consider to hire Bull now.
Grunty 19,600$ (L3, M2, E1, C4, 71): Different starting weapon, small changes at stats and price nearly doubled.
Meltdown 20,030$ (L3, -, E2, C2, 68): Nothing has changed.
Buns 20,188$ (L2, M3, -, -, 74): Minimal changes at stats, but price nearly doubled.
MD 20,710$ (L3, M5, -, -, 58): The hiring costs are doubled and he is now level 3 with small stats improvements.
Fox 24,720$ (L3, M5, -, C1, 53): With her level up she has reached a higher medical level and is a better shooter now. For a starting character her price is now to high. She has the rare starting Weapon MP7.
Wolf 28,084$ (L3, M3, E1, C5, 61): Small changes at stats and big change at price. He starts now with a better shotgun and has still the best traits for CCQ. He is the man for a solo start.
Thor 30,665$ (L3, M4, -, C3, 68): In Crossfire his price is over the starting budget and he has the rare starting weapon G36C.
Raven 33,440$ (L5, -, -, -, 90): Nothing has changed, but in Crossfire her price is over the starting budget. She is a great sharp shooter.


Double Sided Friendships in Crossfire
Flo <-> Biff
Spider <-> Static
Raven <-> Raider

In Crossfire you can find up to three recruits:
1) Jamshed is an explosive specialist for removing landmines.
2) Dariush is a good shooter (He wants a MP7 and a G36C).
3) Roshan has no strengths.
The Quest for the fourth recruit Shenyen is brocken, you can't get him.