One of the main mechanics of Escape From Tarkov is progression.  Primarily players complete quests in order to level up the NPC traders in order to obtain access to better gear.  However, there are numerous other ways for players to progress in EFT, typically giving them advantages over players who have not progressed.

While progression is a significant part of what makes EFT more interesting to play, it also has some significant downsides:

1. Players who have progressed more have advantages over those who have not - which typically makes the game much harder for players with less playtime or have joined the game late.
2. Players eventually reach the end of each progression (and complete all of the quests).  So the developer must create more end-game content to keep these players engaged and periodically reset the progression of all players.

The question I asked myself is whether it is possible to create a viable game similar to EFT but without progression.  The biggest change would need to be to the traders as "levelling up" traders wouldn't exist.  Instead traders would have three tiers of equipment:

• The lowest tier of equipment, basically the same equipment used by the AI Scavs, can be purchased using "Trader cash" which is typically obtained by selling items to traders.
• The middle tier of equipment is obtained from the traders in exchange for items either obtained in raid or purchased from other players via the flea market.  It should also be possible to find this tier of equipment in raid.
• The top tier of equipment is given as rewards for completing daily & weekly tasks for the traders.  (Note: these items would not be considered to be "Found in Raid" and thus couldn't be sold on the flea market.)

Other progressions, i.e. PMC skills and the Hideout, could simply be dropped from the game.  Some other changes I would make:

1. No secure container - all items brought into raid are at risk of being lost.  (Armbands would be considered to be clothing items and not at risk, but melee weapons would be.)  However there might still be value in having "special equipment slots" and allowing keys and other task items to be put in those slots. 
2. No player Scavs.  Player scavs represent a method for players with the available time to make money risk free.  Instead players with assets below a certain threshold would be allowed to purchase (via real money) a "Trader cash" grubstake.  (Which would be what new players start with.)
3. The flea market uses a separate "Player cash" currency from "Trader cash" as traders can buy non-"Found in Raid" items.  Thus players will be incentivized to list items found in raid on the flea market so they can buy (from the flea market) items they need for barters.  This may also help "balance" the "value" of items as players will sell items to traders or the flea market depending upon flea market prices.

4. No storage containers.  The idea is to make the game equal for new players.  Containers allow players with more play time an opportunity to store more items than new players, and thus "put off" the decision on what to sell.  May also need to placing items inside bags & rigs in the stash for similar reasons.

5. No higher priced editions, although there could be an opportunity for players to purchase cosmetic items for real money.

The big advantage to players is new players or players who play infrequently won't be at an immediate disadvantage.  Obviously players will gain experience through play so will have an inherent advantage over players with less experience.  But this is the case for most non-computer games.  New players can also join at any time as there are no progression resets.

The challenge for developers will be keeping those more experienced players interested and providing enough variety in gameplay.  However, in general it will be easier for developers to add new content on an on-going basis as it doesn't need to "work into" the existing quest/trader progression.