Age of Sigmar Narrative/Casual/Campaign Priest/Wizard Promoted Units

Age of Sigmar is a lovely little game, however many Scenarios or Terrain feature custom rules which interact with Wizards and Priests, but many comp packs limit Hero choices fairly significantly, often only allowing 1-4 hero choices. Rules summary is bolded below as I tend to elaborate a lot.

Obviously people who play GW games love their comp and routinely play comp'd (I suggest shying away from comp, it can be quite fun and I trust you're intelligent, you can eyeball sides which are close to even and agree to a fun game with your opponent).

However, comp is good, especially when equating forces across say, a Campaign event where some players might only be acquaintances and while timmy doesn't mind tommy smashing him with his list, timmy might not enjoy tabatha destroying him with her list due to the relationships (or lack thereof) that the players have with one another.

As previously mentioned many Scenarios or Terrain have custom rules which interact with Wizards and Priests however fitting Wizards and Priests into comp lists is very difficult and many factions don't have access to priests, the stormcast don't have a wizard either (as a small example).

Just as a small example the Stormcast Eternals currently have available to them, six warscrolls which don't contain the hero keyword, and as of this posting they have five warscrolls which do contain the hero keyword, with rumours of two more in the form of the knights, and further rumours of another two in the form of musician and bsb. A total of nine hero choices (of course it's possible some of these rumoured choices won't have the hero keyword, but it seems likely based on other existing warscrolls that they will). Meaning if you build your list with wizards (using choices from other factions to get your wizard) you can only play with 2 of the remaining 8 hero choices (as your lord-relictor is also taken as a priest). Personally, I like how the hero models look, they take paint very well and they're all tempting toys to field and play with, many of which will be sitting on the shelf due to these comps.

So here's my proposal for casual/narrative/campaign play:

Allow both players to promote/nominate unit leaders to be a wizard or a priest, wizards promoted this way may attempt to cast or unbind one spell per hero phase and they know the arcane bolt and mystic shield spells as described in the base rules.

A model who is promoted this way cannot be a wizard and a priest, unit leaders work best in my opinion as they're very clearly distinguishable from the rest of the unit in terms of determining when the wizard is slain.

The number and combination of promotions is up to you/the campaign organizer/whatever your heart desires. Possible combinations (not all of them) are included as examples for how you could use this rule:
Both players get one promotion; player A nominates one guy as a Priest, player B nominates one guy as a Wizard.
Both players get one promotion, that must be the same kind; player A nominates one guy as a Priest, player B nominates one guy as a Priest.
More promotions can be awarded in any combinations as long as it's fair (two promotions which much match ie one priest/one wizard for both players) (two promotions which don't have to match ie two wizards for one player, two priests for one player) etc etc.

My personal notes and closing thoughts:

This isn't punishing for players who wrote their list to include wizards and priests, as now they have another source to interact with the terrain/scenario rules which in turn allow them more flexibility as the game evolves (as opposed to their opponent which didn't so now they only have these one/two guys who were promoted).

This allows for more tactical decisions as you are able to interact with the terrain and scenario in more meaningful ways, leading to more (in my opinion) fun and interesting games.

Obviously if your opponent(s) are very laid back you don't need to limit hero choices and can just go hog wild playing however you want, I'm not telling you what to do, just sharing my thoughts.