Describe your suggestion

The End gets a custom fishing loot table distinct from the generic overworld table.

Examples of what might be in it:

• Normal types of fish get replaced by End Fish and some Gelatine
• Lily Pads replaced by End Lily Leaf or Ender Lily
• Other misc. vegetation
• I don't think there's currently any fishable source for the Starshell Turtle
• Water Bottles replaced with Ender Air Bottles?
• Thallasium Boots??

Why would you like this added/changed?

BetterEnd adds plenty of "watery" biomes with aquatic fauna and flora, nice atmospheres (e.g. Megalake, Sulphur Springs), but no really good reason to fish there since all you get is regular cod and clownfish (how did they get to the End..?).

Adding custom loot would give a really good incentive to visit those biomes, as well as a potential renewable source of certain items.

Pretty sure we can make dimension specific conditions on loot tables, but that would require us to remake the entire fishing loot table to separate the overworld and end fish. I love the idea, but I'm not sure I've got that kind of time.

This would be a great idea! Unfortunately I do not believe this is possible... There is only one umbrella loot table that all the various fishing tables go in such as fish/treasure/junk, and it does not care what dimension you're in.