Reminds me of my electoral systems studying days. An electoral system would be referred to as an intexaabii nizaam, plural would be intexaabii nizaamaat. FPTP would probably just be referred to as an acronym. Nonetheless, if I was to give it a designation how about Jo jeetaa woh sikandar intexaabii nizaam?
I'll leave it to other more astute Urdu-daanaan to purvey a more scientific answer to the above. FPTP is a winner takes all system.
I was under the impression that you were seeking an Urdu alternative rather than a transliteration. But yes as with anything in terms of technical vocabulary the safer bet is just to transliterate. I'm pretty sure I've heard FPTP be used as an acronym as well in Urdu news media.
I guess because you asked for a translation and then proffered a transliteration instead. I don't know what the term for transliteration in Urdu is but tarjuma specifically means a translation. So it's just funny that's all. I enjoyed the exercise regardless and am happy with the translation offered.