Overlay video formats: add support for H.265 (HEVC) with transparency in an MOV file?

I know that the overlay function supports using FLV or MOV files (along with PNGs—does the overlay module support PNG animation or just static PNGs?). Since almost nobody supports creating FLVs these days (I tried using VLC to convert to FLV but it defaults to using the H.264 codec, which doesn't support alpha channel/transparency), would you consider supporting MOV files that use H.265/HEVC codec with alpha channel/transparency? Right now in order to do animated lower-third overlays, I have to export them as MOV files using ProRes 4444, which produces *really* huge files—my overlays for a recent project were over 7 GB! If I could save them as HEVC MOVs and use them in ProHD, they'd take up a lot less space! I created some MOVs with a transparent background using HEVC, but ProHD can't see the transparency—all it sees is a black background and so none of the original video comes through.