Just some of my observations and suggestions from playing:
Zombies are way too accurate, even at long range i've been instantly killed by them
Pseudo Giants don't work well in open areas, personally I think they should only spawn in confined and restricted areas like in SOC (same with Burers, when they're out in open areas they're just annoying and not fun to fight) or be restricted to areas that make sense (like the pit in Jupiter with the big machine, if one just patrolled there)
I personally think fast travel should be added (NPC's like Pilot). If this is already in, I haven't found any NPCs offering it.
The Gigantic Bloodsuckers should be removed, not only do they look bad (if you go up close to them it looks like someones just taken the standard bloodsucker model and enlarged it, it looks really angular and jagged) and if they grab you it looks even worse than the standard bloodsucker grab.
Limansk seems like a bit of a mess as a map, I couldn't find the way to the level changer to get to the Hospital as every route was blocked off. This map needs altering to make it more Gameplay friendly and a bit less confusing.
Some areas seem a bit underpopulated with not much to do, like Deadcity.
ideas for features:
Notification of Faction actions:
I completely wiped out the Freedom base as a Merc quite easily. I think it'd be a good feature if there were updates like 'The Mercs are attacking Freedom base' and allies of that faction would come to their aid or a Squad of reinforcements from that faction would be spawned in somewhere to help . it'd also be cool if Faction relations could change. Probably to much for a mod to do but a diplomacy option where they can have ceasefires or ally with/make enemies of groups.
Something that has always irked me in the stalker Games is the way you can just store items anywhere, it'd be a great feature if traders offered 'lockboxes' where they'd store your stuff for a fee and if you stored items in random boxes in busy areas (like the Bar or skadovsk) there'd be a chance of items getting taken.
Zombi u/Dark souls esque spawning system, I really think this would fit in amazingly well with this mod.
Fast travel: Have a tiered system, Stalkers able to take you to 2 maps away max, with the fee being higher the longer the journey and helicopter fast travel.
Basically, at Ecologist/Military or Merc base have a trader option to call one in for a fee which could take you futher than standard fast travel on foot.