TL/DR: Laying down the long-term bet that the full, joined collection of maps will have "zones of influence" for Western vs. Russian loot tables and that the raiders that I believe will be one day mixed into standard scav pools will have the potentional to react to your chosen faction.
Yesterday me (SparkzAlot) and a buddy (TraderGamerGuy) were chatting over patch notes with viewers, discussing potentional impacts and theorycrafting regarding the list when we hit upon what I heartily believe may come to be in the distant future once we we have dynamic loot tables and conjoined maps: rough "zones of influence" for USEC and UNTAR/Bears where one is more likely to find western gear (your 5.56, .308, 9mm Luger options and western gear) while another will have the more (7.62xEVERYTHING and blessed Russian optics). Calling it now that both areas will have the ability to find anything, but there will be a certain skew that show in loot tables and that will add a bit of "home turf" to factions.
Since I believe there will (eventually) become areas that have the chance for raiders to be intermingled with standard scavs, and these "influence zones" will have a higher chance for raiders of their home faction to spawn. To make faction even more relevant and fun, these raiders could act as they do against scavs ignore players (perhaps with voicelines related to running into another previous member of their org. In the hellish tarkovian wastes) unless fired upon. Mixed squads would always be fired upon, thus giving a slight advantage to running with your faction.This could also ease balancing in a big way as specific tiers of Western and Russian don't have to necessarily better than one another – they can be nearly similar in performance/stats but will much more likely to be found within their related fiction's region so that their isn't any meta preference for one over another excepting the ever-OP Dicki Needles voiceline. Think of normal scavs being found to occasionally carry glocks, 870s, Western reddots or ADARs with Magpul furniture while roaming within the USEC zone. There'd be nearly no change in threat or value of the loot from one region to the next for a base scav but this simple regional loot table change would make the standard scavs feel more alive and unique (at least to me)!
Of course, its likely a third zone involving large parts of customs and woods would be implemented with more civilian oriented mixings of shotguns, handguns, bolt rifles, and the holy TOZ. No chance of raiders occurring here as it would be as close to a neutral "starting region" as EFT would ever have.