As I'm myself a developer (and a fan of JA2) I can only advice the developers of JA3 and the publisher: take your time, play your pre alpha game state, think about what is fun and why the original JA2 was so successful. If you do it right, the community will buy and love this game. The other "successors" picked some good aspects of the game and missed most of the rest.
For me the following things are most important (and made the gameplay in depth and immersive):
+ characters, their comments, their interactions, their accent
+ role playing aspect: storys and quests, cutcenes (that depends on players actions), rewards that are useful for recruiting /equipping militia / morr soldiers
+ sound effects, situational music, ambient effects fitting the current map
+ sneak to enemies, your heart beating they will not detect you, position tactically the other soldiers (for interruptions, attacks from the side...)
+ you don't know the position of the enemies, but your soldiers tell you where they here a noise. Especially at night you can use silenced weapons and knifes to kill silently single enemies and then retreat from enemy attention, or even distract them by throwing a grenade in another direction
+ micromanagement aspect: as this is often part of critics of complex turn based games, exactly this aspect (managing soldiers one by one, actionpoint by actionpoint) in JA2 of optimizing the turn outcome with all strategic depth is what makes the tactics part so satisfying. Example: you can use TNT to "open" a wall and change completly the odds hitting an enemy without cover. Or you be on the roof, shoot and spend the remaining ap to lay on the roof to not get hit
