Oh wow, disagree on almost all counts! That doesn't happen very often
1. Bloodwater Entity. I've run both, and while Enigma Drake can get huge in the right deck, it's just a pile of stats. Entity has more play to it, because
reclaiming a spell can be really useful, and the prowess makes sure it can pile on some damage equally well, plus get in for some surprise damage with instants, which means making the right blocks is less obvious for your opponent than with Enigma Drake. In addition, when cubing with the Drake, I found that it's kind of a weird signal into spells matter. The problem is that it does not really further the game plan of that deck. It has quite an aggressive rate, but if you're the spells deck, you don't actually want to play that many aggressive creatures, you'ld rather play creatures that help you stall the game long enough for your spells to take over, or that actually let you cast your spells more often. I found that something like
Rise from the Tides is a vastly superior pull into the archetype.
2. Spell Queller. The reason I would go with Queller is that it seems a more fun card. Reflector Mage is such a powerful bounce spell that it has been bumming out players in Standard and Modern alike. I don't know if any of your players actually play those formats, but it might carry some negative associations. Spell Queller looks to have a bit more play to it as well. It presents a nice mini game, comparable to
Mesmeric Fiend and friends, where your opponent has to choose whether to use their removal on a lowly 2/3 flyer, but get back a useful spell, or if they should use it on a big threat. It also fits nicely into the WU skies and WU flash (looking at you,
Raff Capashen, Ship's Mage) archetypes.
3. Vizier of Many Faces. These cards play in similar spaces, but target different zones. I think the rate on Body Double is just a tad too low. Five mana is a lot for a card that can target only your own graveyard and has no further upsides. Vizier is a little more forgiving at 4, can also clone your opponent's creatures, and comes back for an encore when they deal with it. All around Vizier seems like the more versatile card. If you want to reanimate from your own graveyard, there are way better options in both black and white.
4. Thrashing Brontodon. I've cubed Reclamation Sage for a long time, but pulled the trigger on swapping it out for the Brontodon as soon as it was spoiled. Sage is a respectable Naturalize effect, but it has two major downsides that always bugged me; 2/1 for three is an incredibly bad rate, and more importantly, it's a very reactive play. You feel very bad when you cast this without a target. Now, Thrashing Brontodon is a fantastic play on three, as it has some of the best stats available at that casting cost, and you don't need to feel bad when you cast it proactively.