Went ahead and purchased Temtem, though I'll be waiting a couple of weeks to play since I got so much on my plate. It's fairly expensive ($35) so I hope it delivers, but given what I've seen and heard so far I'm definitely ok with supporting this game.
Also cool to see that Jade Cocoon is something other people played. It was one of my unfinished RPG games of the PS1 era along with Guardian's Crusade, which also had loose pokemon appeal in that you found living toys and used them to battle.
Oh man, I had forgotten Guardian's Crusade. The moment I read that name, I had this vivid image of exactly what the box-art looked like – blocky knight, little pig-thing, pillar of light in the background -- and sure enough, Google confirmed. What a weird memory to have had buried and dredged up. Other than the art, don't think I remember anything about it beyond, as you say, that it was quite fun at the time.