Having different hours for different jobs would unbalance things again. (ie a photo shoot shouldn't really be more than an hour while the diner jobs would be 8+ hours)
How about diminishing returns? The first 3 jobs per day would pay 100%, then each one after would be a stacking -10% capped at -80%. Give the player a message like, "Pay was reduced due to lower performance. A full Rest and Recharge is needed to replenish system functions to 100%." Then have a random chance at a boosted day where jobs give +25% for the first 3. This should encourage more resting. Bounties would be unaffected by this since they can only be completed once per day.