The best way I think I can put it is that outside of Cal's sexual attraction towards Vi, I just didn't feel like their relationship developed enough past what already was established at the start.Vi and Cal trauma is past history by now, I mean there are still some traumas about it but that was a long time ago. They have learned to live with it and moved on with their lives. Now they're discovering another layer to their relationship, sex and love.
Elspeth route feels like if she sees Carl as her port in the storm. She has ghosts from her past to deal with just like Carl, so yeah, I expect drama there because they're broken.
Last point depends on how you play. I have a save being loyal to Els, Carl's monologues are about how he wants to change when confronted with free pussy and he stays loyal..
But both of these occurrences that you two mentioned are consequences of player choices rather than character actions, and only really have effect if you are using walkthroughs and you know that the path you are taking will create a more satisfying story for yourself.It's worth noting that you don't have to have sex the first time it becomes available with the main LIs, so you have some control regarding how fast things get sexually intimate. For example, for Vi if you don't initiate sex in Mallorca she'll eventually initiate it herself after you get home. Only if you reject her then do you end up in the permanent friend zone. Similar branched paths are available for Amrit, Els, and Kana.
I actually just checked, and if you take your time with each main LI, the first time you have sex with each LI is Ch 5 for Amrit, Ch 7 for Kana and Vi, and still haven't with Els. For Ines, we can't really know for sure since her first opportunity for sex was in the Ch 7 (the latest release), but it's worth noting if you don't initiate it there, it doesn't toggle any "permanentfriendzone" variable, which is eventually what happens if you reject the others too many times, so it's a pretty safe assumption there will be future opportunities.
Thinking about it though, the better word to use here is conflict. There just is not enough interpersonal conflict between the characters at all. It's why I think I am interested more into the characters related to Cal's service than the three teens + Kana, there is a hope that something will arise from their shared trauma.