While I'd love to see an overhaul and change of direction in the next expansion (focusing more on having a variety of short-duration and/or quick damage summons, and making a job like the Beastmaster the game's actual pet class), here are a list of tweaks I'd want to see to the current 4.0 SMN that would at least improve our rotation:

Tweaks

1) Bahamut no longer follows the player
2) Tri-disaster and Addle no longer trigger Bahamut's Wyrmwave
3) Bahamut does not despawn your current egi (so it no longer overlaps with Rouse, Enkindle, and other pet cooldowns, and makes the use of Contagion during Bahamut less clunky) -- this may require some potency nerfs to Bahamut
4) Devotion is targettable by player or made a party-wide buff
5) Aetherflow can either be used in DWS, or gray it out so player cannot accidentally use it during DWS
6) Un-nerf Bane's damage reduction. This was completely unnecessary considering the loss of Contagion's extended DoTs and Miasma II.
7) Change Ruin 3 to bring back a 3rd DoT to SMN's rotation. Rename it if need be.
8) Physick turns into Sustain when equipped with SMN job crystal