re the weeing problem - just a thought, but have you tried normal skin shorts with tights over the top? - some years back when I was doing mtb orienteering (trailbreak thingies) I used a simple pair of braces to hold the shorts and tights up (mainly cos I had shorts rather than bib shorts). At least with those you can undo 'em relatively easy to slip them down for a quick pee.
(I think I used to wear tights *under* shorts at one point, but have done the same more recently and it's felt like sandpaper - mebbe the saddle shape's different)
FWIW - Roubaix's great in the middle of winter, shorts+thin tights are fine now in the evening, shorts up to a few weeks ago. Oh, and a thermal under a s/s shirt will probably do from now till it gets a fair bit nippier so long as you're not dawdling
Dunno if you've come across 'em - but have a look at the Corinne Dennis gear - most of it is aimed at women. IFAIA they've stopped making 'em, but I've been wearing a CD women's roubaix-stylee top for years, picked up something similar a few years ago. Pity is they don't appear in many bike shops. Well worth checking out if you can find it, the fabrics are a bit different to the normal stuff available and more snag-resistant.
(And cotton for any exercise related gear is just wrong - gets damp and stays damp...)