What would be your #1 lens request from (full frame) CSC system manufacturers?
Off the cuff answer :
(1) 40-105 f/2. No aspherics, 'bootiful' bokeh, pro-grade build (more Otus than Batis) with 'Batis' resolving power and up.
(2) 180 f/2.8 – The only 180's left are a Nikon D (with exposed rear diaphragm) and vintage Leica-R's (both APO and non-APO). Canon have a 200 which is a 20-yr old design but still a kludge on a CSC
I've never warmed to the 135 FL. Either too long or not long enough. The 70-200's are everywhere but, for me, destroy the svelte attraction and discreet nature of the CSC. No-one enjoys having a bazooka pointed at them plus it's cumbersome. If I'm going that large then I'll go for a 200 f/2 – but I'd agree not an ideal match for a CSC ...