Just tested few games (about 10) on MWS with some friends and I immediately realized that this deck has not any card that wins on the spot so I would cut 1 Mind Twist for 1 Tendrils of Agony.
I found out that after the first mind twist a second one or a third one is pretty useless.
What I was doing was just Mindtwisting their hand, playing out some creatures and maybe Jace and then passing the turn or Time Walking with a few counters.
Having the win now option would be nice so Tendrils would be nice.
A token Lorescale Coatl could also be good.
I can definitely see dropping Mindtwist because as you said if the first resolves you really do not need another one.
Summer Bloom is interesting. It is similar to Exploration which I am pretty sure is not good enough for this list, but an extra 3 lands now is probably better than an extra land every turns just as Black Lotus is better than a Mox. I will test it, but I am not THAT excited about it. It is certainly interesting though. Good find!
EDIT: Upon further consideration Summer Bloom is probably worse than Exploration because it costs more. It is still interesting though.
Another card that has synergy, but is probably not good enough is Save the Momment.
This is the Time Walk that skips your untap phase. The reason that is okay is that you have Jace to potentially reuse and you can Gush lands back to you hand.
You can replay those for more mana which can be used to play more Savor the Momments.
I think this falls into the category of "cool things" which are just not good enough, but I thought I would throw it out there given the synergies with
Jace, Lotus Cobra, Gush and Fathom Seer.