Slitherine

Out of all the special Challenges you can pick from at the start of a Campaign, Heroic Showdown has to be one of my favorites...in theory anyway.

In concept, random Heroes assigned to every enemy unit would add a fair amount of spice that will always be different every playthrough. Constant paranoia about being flanked by camouflaged units; city defenses being harder to break do to things like Aggressive Counterattack, Low Profile, and/or Strikes First; Your font lines being running into trouble do to an enemy or two with something like Double Attack or No Retaliation.
In practice however, for every enemy Unit with an Hero that adds a new dynamic to dealing with it, there is at least 1 enemy Unit with a Hero that does absolutely nothing for the unit. Infantry with Field Repairs, Tanks with Lethal Attack, AT Support on a Fighter, anything with Zero or Reduced Slots. I'm not talking about Units with low impact Heroes, like Thorough Preparation which wears off 5 turns into a Scenario or Survivor which can be annoying to spend an extra Attack to finish it off but is really just a small speedbump, but the Heroes that do absolutely nothing for the assigned unit.

I do feel that Heroic Showdown could use a bit of work to make it really shine. In theory just a few filters or something in place that prevent enemy Units from being assigned worthless Heroes. Maybe have it assign Heroes from curated lists based on the Unit type that lack the unusable Heroes.
Admittedly I'm not a programmer and don't know how difficult setting something up like this would be, but I figured considering it seems a big patch is coming up I figured I'd at least bring this up.

I would use it if I could choose a camo pattern for AI units based on the hero trait. Like red for double attack and the like. That way I wouldn't have to manually check each unit. To me, useless heroes on some units is not as bad as having to check every unit for the hero type.

I did not play with this mode yet, but indeed it's a trait that could be a bit tweaked. I'd say that leaving Zero Slots and other such heroes in the rules is not entirely bad, as if all heroes were purely combat related this could get really silly really fast, but at least the proper hero assignments for classes could be adjusted to avoid useless combinations. This is a bit similar to the recent Limited Stock and Mortal Heroes challenges. They are both great on paper, but in practice should work a bit differently, which only really became obvious as people started to try them out.

I assume for mortal heroes you just stick everything only on ranged units until you get an invincible combo. Which makes it…not as interesting as one would think.

I agree, with little improvements this challenge could be way more fun.
I think that the easiest way would be to set, for each unit class, a pre-set of available heroes.

I would add two more improvements:
- if a unit gets "consolidator" (possibility of +5 overstrengh), do give the +5 overstrengh to the unit.
- give a hero to re-inforcement enemy troops aswell (for now, only units which are present at the begining of the scenario get a hero, whereas re-inforcements appearing during the scenario don't get one)