Bigby's Hand can actually be great against dragons - use the grapple to halt their movement then drag them where you want. Legendary Resistance doesn't apply to contests...
I'm not particularly interested in Eberron but I really like this way of releasing setting-specific material for 5E. It's nice and concise and should be relatively low-effort and thus frequent.
I've played with a Moon Druid at my table. He wasn't OP, just strong. That said, he used standard combat forms, not the grapple-master Giant Crabs, Giant Constrictor Snakes, Giant Toads and so on.
Just make the -5/+10 only be successfully triggerable once per turn, like Sneak Attack. It'll still be worth using, but toned down a bit and you won't get stupid Action Surge nova rounds.
RAW Barkskin absolutely works in wild shape form. Lancelot houseruled otherwise due to balance concerns.
Look at the Druid's background including where they've lived, and discuss with them what animals they would have seen over that time.
Terrible argument.
DM sets the cost of those things, the party can then decide what they want to buy individually or pooling the gold of individuals together, or whether to save that gold for a later opportunity.
LMoP is often considered slightly too deadly if run by the book. The party will probably be thankful for a decent tank. And like I said if you limit rests they can easily run out of wild shapes should you find it necessary.
Enforce the rule that the druid must have seen the animal he wants to transform into, so not giant octopus without good explanation.
Other than that sometimes limit their short rests and this wild shape recharge if you find it to be necessary as you go along.
Do note that a Hill Dwarf could probably be an ok monk tank, or a variant human with the Tough feat. 1hp extra per level effectively makes your d8 a d10, 2 extra makes it d12.
It shouldn't change much at all if the DM keeps the numbers of encounters per rest the same. Mechanically nothing should be affected other than magical items that recharge at dawn (assuming you don't tweak that too).