From what I see you want, you want two commands to do the same thing. I don't know if this works for a fact, but I believe I've seen this somewhere. If this works, you should tell me, because I do not know myself. So as an example I'll be using ulx\lua\ulx\modules\sh\fun.lua
on line 20 according to the default ulx file, it should be local slap = ulx.command( CATEGORY_NAME, "ulx slap", ulx.slap, "!slap" )
If you just do this { } in where the command is entered, both commands will work:
local slap = ulx.command( CATEGORY_NAME, "ulx slap", ulx.slap, {"!slap", "!bitchslap"} )