Slitherine

When getting the opportunity to receive a hero as reward during Onslaught, it would be atmospheric if you don't get a main-hero's faction hostile hero as your pick, e.g. as Filos not getting Falirson or Ailsa, but instead a Transmuter or whatever else is more faction-friendlier.
I'm still no fan of this random seed thing that often gets stuck after a reload with one seed until you do certain actions different during a turn or entirely wait one turn. I normally don't care about goody hut drops, but I gladly make exceptions with unpopular hero rewards.
Priority among hero picks as long as not taken before: faction-friendly > -neutral > -unfriendly. No idea yet which heroes are all possible as random rewards.
Hopefully, something can be done there. I don't mind so much about volunteer randomization as I was happy to get once barbarian trackers with Filos and named them Aelred's Trackers, like the guy in the Curse mini-campaign.

We looked at both options for heroes and while one is more in line with the story (though admittedly the one in Onslaught is a little silly), the other opens up more interesting combinations that you would not get in a more story-oriented campaign, which is kind of fun as well. In this case we stuck with the more interesting game dynamic of new hero combinations.