I know a few people were asking around for this, so here it is. Thanks to the recent silly mistake by SD that generated all those "Champions" that you couldn't hire. I figured out how to summon them, the key is to not use Summon Unit to do it, that would only summon the champion as a unit with the name Champion. Instead, I'm using the quest UnitJoinArmy code, and it works like a charm. Can visit shop, buy equipment, use items, cost no maint, etc...

Here's the code if you're too lazy to look it up:

        <GameModifier>
            <ModType>Unit</ModType>
            <Attribute>UnitJoinArmy</Attribute>
            <StrVal>Rilis</StrVal>
            <UnitClass>Champion</UnitClass>
        </GameModifier>

In this case, I would summon forth Rilis to be my loyal ally. Marriage on turn 1 for male sovereign? Check.