Brentford had to build a TV gantry at their old Griffin Park Stadium a few years back.
Since they knew they woiuld be moving stadium, they didnt want to spend money on what would be only a temporary arrangement, so they constructed a platform on scaffolding just in under the roof at the back of a stand (see above/behind the Bill Axbey banner):
https://c7.alamy.com/comp/C0YHHJ/pic...agg-C0YHHJ.jpg
Not sure how they got it past H&S etc, but the TV companies hated it, not least because in the absence of proper stairs etc, the camera operators had to climb a ladder and then haul their equipment up on ropes!
(Apparently the new stadium TV studio is state of the art.)