You raise some interesting points, but I must confess that it's always bothered me how mercenaries are portrayed in the Stalker games. Contrary to popular opinion, security corporations will prefer to keep a low profile and grease the palms of local officials so that they can operate without being interfered with, or in fact be working for said local officials. This isn't always true but it tends to be the case. Although if you're unlucky enough to be told that next week you're going to be working in Dungholistan or the Undemocratic Republic of Magonkawiwi but don't worry, we've arranged private security to keep you safe, don't be surprised if instead of those well-armed Western PMCs in the glossy brochure you get spaced-out crab-faced locals who look like they'd rape you and slit your throat for your shoes, not necessarily in that order. This subcontracting to locals is done because it's a/ a lot cheaper, local thugs will work for bob-all compared to real mercs, it's basically a form of outsourcing so that head office keep more of the contractual profit, and b/ they don't always (and usually don't) have the available manpower on the ground that they originally promised the client when the suits signed the contract. Bit like call-centres but with Kalashnikovs and Land-Cruisers and very scary-looking people.
I appreciate that the Zone isn't like your normal civil war-ridden failed-state third world cesspit, but even so, and we are told this by Hog in CS, it would make sense for private military outfits to avoid direct confrontation with the authorities if possible, even though said authorities are supposed to be keeping Evil Zone under wraps. Yeah. How much does Lt. Valeri Wankov earn a year? Each merc's private dental scheme is probably worth way more than that. Here's some money, soldier boys, go and play somewhere else. I think that was the general thrust of Maj. Khalestkiy's rant when Valerian had him under lock and key.
I'm not really complaining, Mercs in the game are an excellent source of high-quality weaponry and ammunition as well as a wide range of ancillary goods and consumables, especially when other people shoot them for me. I just think that they should be a little less one-dimensional in terms of character.
Anyway I digress, I did actually have a suggestion. Instead of the usual bring me some supplies, get me a rifle, find my detector yawn jobs, what if any not-hostile-at-the-moment mercs that you encountered gave you an aspect of their job to do? They wouldn't necessarily be breaking operational security, just subbying it out for an expendable local to do and thus minimising risk. I might have a go at fiddling with that, I don't think that would be too hard to do. Oh yeah, MegaDefenceCorp Inc are paying us a cool mill to get mysterious and deadly artefact X from horrible mutant infested area Y but we might get our new suits and guns dirty and we didn't complete the health and safety forms in time, so we aren't insured, but you, hard-up Dmitri Z. Stalker looking for a job, as a temporary subcontractor on zero hours that won't apply to you so off you go and when you come back (snigger) we'll pay you with some shiny boolits and a few cans of tuna. By the way we'll need a receipt before you go so we can claim your reward back on expenses.
Another idea which I did in fact implement myself was Mercs advertising on the PDA when i created different channels for the various factions. Subby jobs like the above and also full-term contracts for the right applicants, medical care, dental, pension scheme and sharesave, performance bonus, paid leave. It's a good offer, with the downside of being shot or eaten or torn to shreds or worse, but anyone who's already in the Zone has to deal with that on a daily basis anyway.