For Land Druids, don't hook them to one type of land, instead, they connect to the land in general. In game terms, the land druid adds a land category spells to his prepared list while he is in the corresponding land type.
Flexibility depending on locale without being overpowering.
I like for monsters to have at least one unique active or passive ability. I often pull abilities from 4e, 13th Age and two 3rd ed template books. Some things I do...
1. passive- auras or abilities triggering when advantage is given to creature
2. active - activated when monster hits opponent...
Feats? Eh, I like the thinking upthread about how some of the current ones should have been folded into classes or things anyone can do. I suppose there is still room for a few more feats, though. Balance is key...
I'd rather have more warlock invocations (more like the 3.5 ones, please) more...
I have done this a few times...I dont think I successfully captured the experience I was going for though. I still think it could be done, but prolly should be reserved for more episodic games or those trying for a pulpy serial feel maybe.
I have one a green and gold (sure about the gold but the green, well im a little color blind,) d20 that I've had since my very first session in '94. It also has a peculiar quirk that seems to result in an extreme amount of both 20's and 1's equally...No joke! I only use it these days as dm when...
I've added items that can trigger inspiration earning, such as a green dragon dagger, which offers inspiration for an instance of betrayal, mirroring the green dragon's tendencies.
I agree that inspiration needs something more. Either more hard baked into character creation, or even possibly...
Ive always been a sucker for monster books, but at this moment, I would love to see a monster toolkit, with powers and themes/4e style templates so one can customize already existing monsters, or build new ones whole cloth. There could even be example creatures included.
I loved truenamers, and especially the ease of how the actual utterances functioned in play. I'd suspect they would actually lend themselves quite well to 5e