It’s really simple to create a 1080i50 signal from a 1080p25 sequence. That said, you’ll need to take into consideration whether or not you want your program to stay progressive all the way through. Meaning that there is a motion difference between any DVE moves, title rolls/crawls, wipes, pushes, etc. In 1080p25, these move in 25 steps/second, in 1080i50, these move in 50 steps per second (quite a bit smoother). Some broadcasters require titles be done in 1080i50.