Bomberman appears in OS's version of Brawl. But what kind of character would Bomberman be?
First of all, Bomberman's fighting style would focus around his trademark bombs. He would be able to pull bombs out of nowhere as his default B action and kick them around with B-Side attacks, which would do minimal damage in of themselves. The number of bombs in play at once would either be limited by a counter (probably 3 to 5) or be limited by their detonation time. Either way, bombs will go off eventually even with no input from the player, causing area damage that can also hurt the player. Whether the bombs can be detonated at would determine the character's playstyle.
Bomberman would be a fairly light and weak character if it weren't for his explosive arsenal. If incapable of controlling when his bombs explode, Bomberman would be best at fighting multiple opponents on smaller stages, making him less likely to be accepted by the more serious part of the community.
If, however, players are able to control detonations, Bomberman would be a fairly powerful and distinct character, capable of controlling the field of battle. In this case, larger and/or more complex stages would give him time to set up "forts" of bombs, making him also a defensively capable fighter. Furthermore, by dropping bombs by a ledge, he could even counter ledge-grabbing, a very interesting ability.
Overall, Bomberman would stand out from the Smash crowd in this timeline, but depending on exactly what his moveset is, could have a nice private niche.
Tom Nook replaces the Animal Crossing Vilager in this timeline; how exactly would they differ?
Quite a bit actually. The Villager of Animal Crossing is portrayed as a hard-working if happy laborer who is out in nature gathering resources. Tom Nook is a crafty businessman with helpful nephews covering his flanks.
Therefore, the logical position for Tom Nook as a fighter is as a man with a hat of tricks. Every different attack should involve a different item or piece of equipment is possible. Perhaps his default special attack would be summoning a Smash Bros universe item, even when Items are not set to generate. This could make Nook the least predictable fighter.
Also, Tom Nook can use a mechanic based around his getting richer. Similar to Phoenix Wright gathering evidence in Marvel vs. Capcom 3, fields where Tom Nook plays can have Bells scattered about, which empower him and ONLY him as he collects them. The richer he is, the better the weapons he uses to attack are.
Tom Nook is a weird character, much like OTL's Villager. There is a lot of fun to be had with him.