I think the main positive effect could be saving server costs, maybe, would like some input from the team. Did you talk to them?

I am not buying that bots are renting tons of cheap cards, they mostly play with soulbound reward cards and just happily play each other in wild bronze to gold. If you dont believe me make a new account and play wild. I did it for science and to see how bad it is and I haven't faced a single non-soulbound card until 2200 (where I stopped out of boredom).

Mainly this will push the price of CL rentals, after all you can rent some useful CL cards for under 1 DEC, even at max level. Whether this is a good thing, who knows. I would be curious how much DEC is burned by listing unrented cards. Effectively people stopping to try could mean less DEC is burned, whether this is worth the saved server costs, I can't tell.