The best way to play Hitman Freelancer is to maximize the doable Prestige and other objectives for mercs to start with.
Choose the big, easy maps for showdowns which aren’t alerted territories - Berlin, Miami, Paris, etc.
Do all the alerted territories first.
Take your time.
Fish for driftwood, with encumbrance of zero, for emetic poison in your suitcase. Carry a banana especially if you don’t have silent assassin objective and to hide bodies.
If you have caught a fish or if you find a mushroom near the shed, you can make a lethal and sedative vial, which you can make into free syringes with a contraption in your med bay room (if you have advanced so far to the level).
If a courier or safe is difficult to get without losing objectives or possibly getting killed, just complete the mission without completing everything.
I am at Level 81, have the complete set of weapons and other items on the wall and >500,000 mercs.
At level 81 you have 15 slots, which means that you can carry everything you want in the mission, and any disposable you use in the mission (e.g. explosive, electronic key card, sedative) are use in the mission, appears in your chest at the end of the mission.
I used to always take the silent assassin / suit only prestige objective, but now I don’t need the mercs, so I focus on completing all the challenges.
Hitman Freelancer gets easier, both because you get better at it over time, and you don’t really need to mess with complicated objectives just for mercs anymore.
Hitman Freelancer evolved from ghost mode and elusive targets, and it is likely that IOI will optimize and create a Hitman Freelancer like mode in Project 007.