Has any workaround been found for this?

You should be able to edit it in the disassembly bytecode. Maybe the following steps:

1. call it as a global function (center_camera(0, x, y))
2. Switch to Disassembly tab
3. Change the following bytecode from

call.i center_camera(argc=3)

to

call.i @@This@@(argc=0)
push.v builtin.center_camera
callv.v 3

4. Type "center_camera" into the tool search bar.
5. Delete the bottom result from Functions.

Any way to do this through the CLI? Using Linux.

Try Wine or a Windows VM if you can. It might be possible to script, but the assembler isn't as open as the compiler.
Wait, there are ExportASM and ImportASM, right? You could use those. Deleting the function should be easier to script too.

Does the workaround still work? While this solution does make the code compile, in-game, it's just causing a "Variable not set before reading it." error.

The only reason I could guess that happening is if you also edited the function's definition and it broke as a result. At that point I might just recommend using a user event or global script.