The wizard has spoken, and I've come around. I'll support testing out moving to just season rentals. Ideally, the conditions should be (1) that it's easy to implement (therefore probably should do the 14-day rentals rather than actual season-level, which anyways I think is fairer as people won't try to time their rentals based on where we are in a season), and (2) we should be open to reverting the change if we feel it's caused unintended negative consequences.

For other folks who were against this change, here's a summary the pros and cons of moving to only season rentals:

PROS
(1) Fixes the various exploits that have been discussed above
(2) Ensures a rented card cannot be used for significantly more energy than an owned card, thus giving value to ownership
(3) Potentially improves user experience by ensuring there are MORE cards available for long rental periods (i.e. 14 days), so players don't have to worry about having their rentals cancelled or having to re-rent every few days
(4) Reduces transaction volume and server load significantly (per Matt)
(5) Helps mitigate concerns around minimum rental prices (per Matt)
(6) Removes confusion around daily vs season rental in Survival Mode (per Matt)

CONS
(1) Increases up-front cost, reducing accessibility for users who just want a taste
(2) Reduces flexibility (e.g. wanting to only rent for the weekend)
(3) Increases cost for those renting for brawls/tournaments (however I'll point out this ensures you'll be able to rent BEFORE a brawl/tournament and not have to worry about getting cancelled on, so there's an upside to this one too)