Both are valid concerns. The way I see it, this could be an answer to both.
A) With this, the five character thing may be jarring to some. However, that's the thing. With something like DLC, buying it is optional. And the resources are already seemingly there. It'd be a less complicated addition, so it'd be worth the time to get some extra money.
B) With the Final Smash, it'd only take a model swap. The very first trailer showed a pre-Alfonzo Toon Link Train. This is changed if Toon Link fights. Similarly, if Chrom is in a match, Robin's Final Smash is altered. One option could be Frederick as a replacement, only needing a galloping and stabbing animation, plus "Pick a God and Pray!" If Chrom's not in the match, the Final Smash can remain the same. After all, Chrom is close enough to Robin that appearing in his Final Smash isn't out of character, either.
All in all, optimism is what will keep us going. As long as we can provide solutions, no matter the likelihood, we'll help get our voice heard.