Does anyone sleep in down trousers and jacket as an alternative to using a sleeping bag?

I've got a light down jacket which has been mint to use with a 3 season sleeping bag in the depths of winter to keep toasty and save weight on carrying a warmer bag.
I've been pondering about getting a point 5 half sleeping bag from alpkit to supplement the legs in depths of winter and maybe to use on its own with the down jacket without a sleeping bag in the spring or autumn months,
then it hit me! Why not just use a pair or down trousers? I've enjoyed the extra warmth about camp with the jacket so it would be useful to be able to do the same with the bottom half.

Any reason why this wouldn't be a good idea? The only draw back I can think of are of potential cold spots at the waist and cuffs etc but that would be the same as using a half bag. I'd obviously have to not get them wet but same precautions with using a bag really.

I've got a fair few long and light trips planned this year and I like the thought of keeping the weight down whilst being able to throw on a jacket or pair of trousers when stopped for breaks / food etc.
Pair of down socks added into the mix for the win!!

I sometimes sleep in Integral Designs Primaloft trousers but with a bag / quilt rather than instead of. I like to have something over me when I'm sleeping ... probably some deep seated childhood insecurity or some such

I always struggle to sleep without something covering me even if it's just a sheet.
Even while in the mob, I always carried a sleeping bag liner at least to doss down in.

I remember following a blog about a cycling piano tuner who was just using PHD down jacket and trousers inside a bivy bag for minimalist kit. http://www.piano-tuning.co.uk/blog/

I too need something over me to feel comfy.

I used to sleep in bivy bags and down clothing (I needed anyway for belays) when winter mountaineering. Uncomfy way to shed grams...
Bikepacking is different as you don't need down pants anyhow except in your case for camp. But then I question the need for down pants for camp any other time than winter... and even then... and don't you think it's likely that you'll have a fire going when it's one of those long nights in camp?

Here some numbers. My very light down pant weighs 220 g. My lightest down top 220 g too. That's about 50 - 60 g more than my quilt that'll keep me warm to about 0 °C without more than summer riding clothes. My smock and pants probably would keep me warm down to about 8 °C max. Even with an additional space blanket (lightest being about 40 g) I guess I'd have a miserable night at 0°C.

For the lightest possible summer setup I think a lightweight quilt or pied d'éléphant is very hard to beat.

Just what goes through my head thinking about past experience.

Seems there not much weight in the mix. Might punt for one of the point 5 half bags so I can double it up as a sleeping bag for the dog in winter!

I always think that as long as you're going to be carrying a mat, then a quilt makes more sense than a half-bag ... I understand this won't be true if you're sitting out the night on a mountain ledge but when you're lay in a field.