There is no new disguises feature in Vengeance.

Bobby Ray's is a business and runs independently from your merc assignment. The plane that airdropped you doesn't work for Bobby Ray.

Vengeance has a number of local RPC's to recruit, first see if you can try locate new recruits that were scattered after Omerta fell and the training base south of there.

Vengeance also encourages guerilla style tactics, and may be necessary early on the game, the Arulco of Vengeance is generally less friendly than the one in Vanilla. You may just have to consider more hit-and-run tactics to begin with and steal weapons when you can or pry them from the dead hands of your enemies. From personal experience I ditched Drassen early on with the oncoming counter attack, but found things easier (though never easy) fighting further West and establishing my first base at Oronegro.

Choice of starting kits/gear is also quite an important factor, when first putting your team together, and is advisable to choose at least a couple of mercs with some good weapons. You can save money from using some of the cheaper Mercs with the melee trait that seem very effective in the early game, such as Blood, Razor or Arsenal being very adept with throwing knives or shuriken.

Don't forget Tony is still trading in San Mona, though he also takes time for his inventory to improve as the game progresses.

Revenue can be acquired from other sources just like in Vanilla JA, such as looting bodies after a battle, or completing some of the quests, including some new ones specific to Vengeance.