I'm glad most of the creatures don't respawn (expept spiders, I believe). It's only consequent since berrys and bushes don't respawn either. As often as you travel the map and take the same routes over and over again, it would be annoying to meet (and fight) the same creatures all the time. I remember one title of the Far Cry series, where this was the case. Just repetitive and boring.
And regarding your other wish:
(from the Coffee Stain Roadmap)
Further down the road - TBD
• Improvements on core gameplay and systems
• The rest of the FICSIT Milestones and Tech Unlocks
• More buildings, parts, vehicles and creatures