I need to remove Symbols from it. It could be in any unorthodox way possible, but it needs to be done. Later I need to replace said functions with equivalent ones from .o files.
That is not possible if the ELF file is a EXECUTABLE and was not linked with --emit-relocs as it's impossible to reconstruct where the symbols are used.
You need to find and fixup all references yourself, IDA can tell you where most references are and even has a patch function (although manually assembly is required). This won't work that easily if relative branches were used, that may require using a constant placed in the literal pool.
Edit: You can also just append your modded functions to the ELF file and patch the main function to branch to the modified ones.