We have the option to retire and unretire a character, we also have the option to learn and unlearn skills/spells. Why can't we have the option to retire and unretire minions.
This will give us more ways of tweaking our strats, trying out strategies from 4 minions to 3 or less minions. But, off course there will be penalties for retiring/unretiring minions just like when we unlearn skills/spells, say 2-3% off from whatever learned spells/skills on the retired minions and also probably a 2 days waiting period to unretire the minion. However, when you retired a minion from a 4 minions team and you later hired another minion, your retired minion will be automatically fired.