[HELP] Passing interlaced content

[r3dfx]

Hi! Is there a way to pass interlaced content w/o deinterlacing it? The only option I found was overwriting scan type to progressive but that would require adding at least AssumeTFF somewhere up in the chain...
I need to re-encode FFV1 422 interlaced to x254 420 interlaced with proper interlacing handling to avoid halving my chroma framerate due to improper 4:2:0 conversion