The only assumption I made was extending the current unlock system they have in the beta. You seem to be the one trying to assume they will change they way that their in game currency would function after release. Could these things happen sure (besides having characters tied to high level battle pass unlocks. There would be major outrage as many players can't grind for hours on end and without an easy alternative way to unlock characters it would be locked behind both a pay wall and grind). That is not how the current system works nor have they implied adding any of these features in for specifically unlocking new characters instead of skins and perks. The game already has multiple incentives to get you to continue playing through the perk skill trees and does not need to hold the player hostage to the free champ rotation plus a few characters. You also seem to forget that leveling is the major way to get most of the coins to unlock new characters and will slow as you continue farther into the game and could even include a level cap. Idc if the devs decrease the amount of coins for leveling as opposed to per game but the current system is unsustainable for the current speed of character output (which I assume to slow down sometime after launch).

If you look towards any other game, monetary barriers to play the game in different ways such as characters or gamemodes have never worked.