not perfect like a true ettr mode but I find uniWB in Av get similar results. Guess you could experiment with turning up EC+/- if shooting scenes where the correctly exposed pics histogram is shifted right (eg. predominantly/exclusively sky compositions at dawn).
YMMV but I found this works well enough for me as there is less bias and underexposure than vanilla WB (as far as raw goes obviously) since there is no RGB multipliers and histo clipping mirrors raw much closer than vanilla wb which is jpeg data made with multiplier values in the channels to generate a jpeg which often means good looking exposures are actually a stop under in cr2.
I only use timelapse for star stacking (dss and registax) so always in M never Av so no experience of how it may work out for long timelapse stuff on night to dawn/dusk transitions where obviously some semiauto exposure may be more useful but thought I'd mention it in case not tried that approach.
YMMV but I found this works well enough for me as there is less bias and underexposure than vanilla WB (as far as raw goes obviously) since there is no RGB multipliers and histo clipping mirrors raw much closer than vanilla wb which is jpeg data made with multiplier values in the channels to generate a jpeg which often means good looking exposures are actually a stop under in cr2.
I only use timelapse for star stacking (dss and registax) so always in M never Av so no experience of how it may work out for long timelapse stuff on night to dawn/dusk transitions where obviously some semiauto exposure may be more useful but thought I'd mention it in case not tried that approach.