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.
I actually created the account @pointonedec and fed it a ton of Single BCX CL cards and others that rented consistently for .1 DEC
The ROI was bananas but as things are changing it started coming down so I added in some RB cards to bolster the falling ROI.
Eventually I abandoned the project and I am simply waiting for the cards to come off rent so I can transfer/combine/sell them.
By doing this and renting these ultra cheap 1 BCX cards I saw most of the rent names were obvious bots with names like abc123, abc124, abc125 etc vs my other accounts where I rent Max Level CL/RW/RB cards and the names were JohnnyBoy69 or TomBombadil1975 - as in actual players :)
In the end, this experiment and data gave me the idea to make this proposal which would then force the Bots to rent at 10x their costs.
I think the pros far outweigh any cons and for the actual players who rent cards 1 DEC, even with DEC at peg is still only a tenth of a Penny or $.001 😄