Synthetic fleece replacements (e.g. patagonia nano-puff) are expensive and are essentially wadding between two windshirts (and you probably already have one of them):
some wadding comes attached to a polypropelene scrim: so why not sew inside a polypropelene workware disposable "lab coat" (scrim forms inner jacket shell), to make light insulation jacket which can be protected by your usual windproof shell.
wadding that is without a scrim could use two polypro jackets, one as outer shell, one as inner.
Easier options
would be
1)to not bother with wadding insulation in the arms.
2) For a bodywarmer: Scrimmed wadding could be doubled up, one scrim as outer shell, the other as inner (i,e . no need for the polypro jacket(s)). Cheap and easy.
(example of polypro coats: http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2290586)
