Starting with the Update Aquatic, many blocks in vanilla Minecraft can co-exist with water source blocks. This includes vanilla chests and ender chests. However, EnderStorage ender chests will displace any water they are placed into and cannot become waterlogged after being placed, either.

For consistency with the corresponding vanilla block, for decorative purposes, and for consistency with other item/fluid transportation options (e.g. Pretty Pipes, Immersive Engineering fluid pipes, Applied Energistics cables), it would be nice if ender chests and ender tanks could be waterlogged.

Sure. I don't see any issue with this. I'll leave it up to @covers1624 as to when/if it gets implemented.