Question - Not an issue. (Mappings)

[Cinnaminin]

I do not have much knowledge in proxies, but I wanted to ask a question:
I'm currently backporting a bunch of blocks from 1.21.11 to Legacy because i want to play on me & my friends server on LCE. My current issue is the mappings. Right now im testing with the Amethyst block, but I have found out that Block IDs are no longer a thing since "The Flattening"

Basically I have my Amethyst block on legacy coded to use 174. BUT I have noticed that there is already a mapping for 174 in blockmapping.js
To my main question here:

• Should I as the one backporting use numbers in legacy higher than 255 (last ID in java) to escape conflict?
• For you the developer of the Proxy, is there a way you can implement another mapping system for users to add mappings such as LCE:JavaString
  Which in my case would be 257 (new amethyst block ID in legacy if needed to be changed, currently 174) and minecraft:amethyst_block (257:minecraft:amethyst_block)

Thank you for any of your time!!