You can do that, but they will not have a solution also. The problem with interlacing has always been and will always be the horizontal lines. As from the nature of interlacing TV lines will only update with half the framerate. So in 50i every line updates 25 times a second. in 50fps it starts with the uneven lines, and when it’s done it updates the even ones (1, 3, 5… and then 2, 4, 6…) So if your graphics contain lines of only one pixel height or edges that fall on an even line, it will flicker with 25Hz and you can see that. In SD that was a huge problem in HD it is not so obvious. That is why you do not see the flickering in 50p, as the lines are updated progressively (1, 2, 3, 4, 5, 6…) 50 times a second.
You have two solutions now: Go with 50p or change your graphics with interlacing in mind and stay with 50i. Nobody will tell you any other solution.
By the way: Camera pictures also flicker when you shoot a horizontal line raster and the lines fall precisely on the TV lines.