Why tap that creature? It's an instant effect, so I don't think that achieves much. Also, we already have...
Including the fight effect would make this really similar. Plus, that still has the problem of the token not being to able to benefit from one of the modes. You could change the wording to "Up to one creature you control fights target creature an opponent controls."
That wording is also not in Magic. I mean it’s a custom card so we can write any wording we want. But if we want to keep the card simple, elegant and within the perimeters of what Magic normally does, then we can’t go with “Up to one creature you control”
Am I wrong?
I can’t remember a single newish card with that wording.
The tap was to bypass that problem. That is not unheard of in modern Magic.
Of course we could just make it a target effect but then we are not pass the problem of being able to utilize the creature token that was just created for the effect like we were trying to.
Option A: Keep the card the way it is. The +3/+3 cannot affect the newly created token.
Option B: Make it a fight effect usin target. The fight cannot affect the newly created token.
Option C: Make it a “Put a +1/+1 counter on each creature you control.” The ability will affect the token. This ability has not been used very much in green (but has been used a lot in white) but it is not unheard of. The latest card was
Song of Freyalise. The double effect we have seen on
Strength of the Pack very recently.