I have thinking this problem with seamstress and she said that it should be possible. Although we disagree from 'ass area'… :)
Put on ordinary, tight and non-stretching fabric pants. Do some squats and you see problem areas that has to be solved – these are your buttocks and your knees.
1) Your buttocks is tightening fabric from 'ass area' and also from front of the thights.
2) Your knee is tightening fabric from front of the knee.
1 plus 2 lifts your trousers up, exposing ankle.
Soldiers in that Obama photo are using 18th century "overalls", but they may not to be 100% historical accurate, but use photo as inspiration. If you solving problems 1 and 2, then your trousers will get shape of 18th c. style, AND they get more uggly than in Obama photo.
Here is my solution:
1a) Your buttocks area must have extra fabric, making trousers baggy.
1b) Because trousers get baggy from behind, it may cause problems, example making fabric saggy behind your thight.
1c) To solve saggy fabric, trousers have to be 'slim fit' from the thights.
2a) Front of the knee is needing extra fabric.
2b) To solve this, you can make some kind of fabric folds to knee area (trousers front piece), or something like that.
2c) Fabric may become saggy from front of the knee, but I don't think that it is problem.
2d) Because your trousers are almost skin tight in your thights, it may be better to make trousers slim fit below the knee or your trousers will look very weird…
Ankle area should look like more or less like Obama photo, maybe little tighter. You may use shoe laces behind ankle to make fabric tighter in the ankle area, and it gives some flexibility if you use different shoes.
You can sacrifice 10 dollars to Overalls pattern and modify it if you want. There is two types of breeches (and overalls) – with fly and "drop front". Pattern below seems to be with drop front.
http://www.amazon.com/18th-Century-Military-Overalls-Pattern/dp/B002O7DN2E/ref=pd_sxp_f_pt
There is many historical breeches pattern in the internet, but if you are intrested, I can email some pattern material to you. From breeches pattern, it should be fairly easy to make full Overalls. !!!! Pattern of historical trousers/breeches is totally different than in modern trousers!!!!
Two things to remember:
1: your trousers will be ugly.
2: sew first trousers from cheap fabric