Even the Canon X0D bodies you can change out the focusing screen but I don't think there is a split screen. As long as you don't have the 240k pixel screen you shouldn't need an additional screen for focus adjustment.
Now if you were planning on doing video with the Zeiss or older lenses that would be different. I think I would like to use a screen then.
It would be cheaper just to get another AT-1 I bet.
2000 740i-Annalisa and 2008 335i-Weebl. Weebl may wobble but has DTC
2012 X5d in Sparkling Bronze ( The Ultimate Cat Carrying Machine)