I considering a 1.5 deg angleset for my 2017 T129, which would make the geo within a whisker of the new S120 as far as I can see.

The bike is fitted with a FAS no. 57E ZS integrated headset – so the headtube is 44mm ID upper/ 56mm ID lower.

I *think* that this works headset would fit – link

It has a ZS56 lower cup, but an EC44 external upper cup – I don’t think that is a problem (in fact I can’t find an angleset that would fit with ZS cups at each end, so I guess it may be necessary).
I’m not worried about the extra stack height, but is there anything else I should know?