Mod Ideas

weapons of mass destruction.

1. A block that functions as a checkpoint, at least for the player's position. It is initially deactivated. After being pressed, it becomes active and changes it texture, for example. If at least one checkpoint is activated, pressing a certain key on a keyboard instantly teleports the player to the most recently activated checkpoint. The more minimalistic and simple — the better.
2. Abstract simple megalophobic structures (like pyramids) appear randomly far from the world spawn point.
3. Villagers may rarely attack the player at a random moment.

4. A bit off-topic — not sure these are ideas for mods specifically; they’d probably be easier to implement as website services. Still, I think they’d be pretty useful if anyone feels like programming something:
a) Click on an image with an eyedropper tool (like in MS Paint) and get a list of blocks with similar colors.
b) Enter a distance and desired column thickness, and get options for how many spans and columns are possible and what the span lengths would be (for example, for a distance of 23 blocks with 1-block-wide columns you could have 4 spans of 5 blocks separated by 3 columns).

Small flying cows

Self explanatory

A few chunks in the ocean just go down into the void

I'm not sure; some of these mods may already exist:

1) Highlight another player's elytra flight path for a few seconds so you can fly exactly like them (through rings, etc.).
2) Wardens react to sounds picked up by the microphone.
3) Direct sunlight deals damage.
4) Swimming is disabled.
5) Gravity changes at random moments.
6) Flowing water emits a babbling sound; the more nearby streams, the louder it gets (up to a limit).

7) Parachute, flashlight

your items launch away on death. like, a LOT farther

take a crop, like an apple, orange, potato or mushroom, then make a cute pet themed around said crop. give it a purpose, like does it help you mine ores? fight mobs? carry items? farm potatoes? then pick how to find it and tame it, like is it found in the wild? sold by villagers? seed found in chests?

rinse and repeat a few times and you can make a cute pet mod.

Floating islands that generate alongside vanilla terrain

flying steves

goats and throats