I think I'll spend this week on the Latios escalation and then next week farming coins for Zygarde/Azelf. Pretty much abandoning the new main/expert stages.
Quick calculations on the special shop:
Weekend Meowth Jewel = 3 additional tries = ~15,000 coins per Jewel.
Conversion of Jewel to coins: 12 Jewels for 48,000 coins = 4,000 coins per Jewel (but you need 12 Jewels first).
Unlimited hearts for one hour = 2 Jewels.
Assuming you can do Meowth in 2 minutes and average 330 coins per attempt: 30x330 = 9,900 coins. Subtract the 2 hearts you get normally: 28x330 = 9,240 coins = 4,620 coins per Jewel.
Let's say you're insanely good and can get 530 coins per minute. 58x530= 30,740 coins = 15,370 coins per Jewel.
Double heart regen for 24 hours, 10 max, 6 right away = 2 Jewels.
Assume you never "waste" a heart = 4x24+6 = 102 hearts.
Normal heartrate = 2x24 = 48.
Bonus 54 hearts. Spend them all on Meowth: 54x330 = 17,820 coins = 8,910 coins per Jewel.
TL;DR: Unless you're incredibly good at Meowth, spend your Jewels on extra Weekend Meowth attempts.