Wait, do you want to make 4k BDs or will regular 1080p work since you said you don't need UHD (aka 4k)?
Because there are plenty of tools for BDs, but I think for 4k the only consumer level tools are still paid. The other question is if you need the extra space, because 25gb discs are cheap, but dual layer BD (50 GB) are xpensive. BD XL discs in dual and triple layer (66 and 100 GB) are practically impossible, and very expensive. You might be better off sticking a file on a hard drive and using the media playback features instead.