16384×16384 seems to be the maximum. I don’t know what program football stadiums use for videos shown on fence screens. Premiere Pro seems rather limited.
Are you making a video that’s 125 screens wide? An average 1080px wide screen is about 1 metre wide so your footage will be shown 125 metres wide – thats an entire football field. If you’re gonna chop it up, there might be a better way. I fear that the file size will be huge and may take a week to export – make sure your computer is cooled properly and can survive a blackout.