When it comes to Tom Nook's motivation for bells, he is professional at in the money making business. For me, it is easy to imagine that Tom Nook would be motivated to fight in combat if it meant bigger profits on his end. For that reason, it is easier to imagine Tom Nook fighting than Isabelle for me. Although, it does not mean I think it would be harder to create a moveset for Isabelle, it's just easier to picture just based on Tom's fan-depicted characterization:
See, I don't think that's an accurate reading of the character.
Tom Nook is a clever and shrewd businessman, yes, but he's never getting his hands dirty if he can manage otherwise.
He sees you looking all desolate in town and what does he do? He makes a calculated risk that becoming your renter will pay off for him a lot in the long run because you'll want to increase your house size.
Doesn't mean he's a bad guy, though, and I'd imagine he wants the best for you, both as a client and as someone he took under his wing.
He sees that he can make money with the situation, but he never actually does the hard stuff himself. He signs contracts, finalizes plans, and submits paperwork, but he prefers to be doing it all in his store if he can manage it.
And I think there's a reason for that. He's implied to be Timmy and Tommy's dad (same species, all have names that start with T, all work at the same place in some games, the kids seem to have inherited the family business while Tom branches out into house construction), and it seems he has a busy home life with them on his hands. He's trying to support them and teach them to be successful the the world, particularly the world of business.
Note that he has them doing a lot of the heavy lifting even in the first game. They're at the furniture place, while he's the one taking care of selling essentials like tools, stationary, and gardening supplies. He wants them to learn the hard parts of the job like moving stuff and convincing customers that they really do need a fourth bed. And he's gotten them trained well enough to place his trust in them to do what he needs them to.
That said, he's not
evil. By no stretch of the imagination is he malicious. A little greedy? Yeah, probably, sure.
But he has a clear moral code that he abides by; he even actively displays displeasure with Redd because of his less-than-honest business practices, iirc. This isn't a man who values bells over people, and he intentionally cause another person harm, even if it would benefit him financially.