Lucidstuck II

Here's my suggested loadout

spy mutli-tool in the form of a phone, silenced weapon, fulton system from Metal Gear, radar, explosives.

The multi-tool is a given, the weapon will let us take out guards and get a disguise, the fulton will let us dispose of bodies easily and possibly deliver our objective quicker, and explosives are always helpful.

the fulton thing wont be useful if we go inside. silenced weapon is ok, but we might be able to do better. depending on how it operates (RL silenced vs movie silenced), it might still be quite loud.
I would instead suggest a compact crossbow. not only is it quieter, but you could also use it to fire hooks to climb stuff, or even retract shot guards to get them out of sight immediately.
instead of the fulton I would say a disguise. a couple clothes should fit in the briefcase and should help us blend in, at least from a distance.

and what exactly do you mean with explosives? like a brick of C4 with an adjustable timer or a bunch of grenades?