Just a couple of thougts
Low league players have worse reward chances, earning crédits and potions with dailys, not to mention end season that with new adjustments only counts for current league, so forget about earning power with reward chest. Solution rent cards and keep grinding. Also every time cards give less and less power.
Next problem, cancelled rents and higher rents as season come to an end. I think that there should be a penalty to whoever cancels a contract, it is very frustrating to see your season rent being cancelled and that they are now at a much higher price on the rental market. I understand that this game works on a free market, but free market also needs to work on trust between buyer/seller. Once that hand are shaked there is not turning back. Maybe adding an option for "guaranteed time Rent" that cannot be cancelled and could cost some extra dimes. F.e if card is rentetd at 0.10/day I guarantee a 0.15/day x 15 days no backin from either side. Time límit should be also agreed by Owner, preventing extra long time renting allowing owner to rent at higher price if market allows.

Bottom thing, canceling rents at any time is not cool.
And grindding is getting grindier.
Remember what the wise guy once said "kids of today, are grown ups of tomorrow" (boy don't grew really fast?) Lets try to don't be so hard on us new arrivals...