Rosthwaite/Seatoller(Borrowdale) upto Styhead and down to Wasdale wouldn't be favourable with bivvy kit IMO, just for the uphill. I don't know what 'good' options there are around there. Might be a carry up whichever route you choose?
Probably the longest 'don't screw up, or you're over the bars'-technical down I've done. A great down, though I had in my head that it had hospitalized one of the magazine's staff some time ago (I think they may have been on a lightweight hardtail but .. )
Sty head south to Wasdale I've never done, I seem to think an old STmag article (same one as mountain rescue/hospitalisation) said the most south easterly of the 3 b.ways was pretty good, though can't remember what the wording was. Something like issue 26-31ish I think, at a guess 27? or 28? maybe 29? ..
Geograph isn't showing a lot
(part of) Borrowdale upto Styhead
Styhead down into Wasdale
Move around a square or two
A few of mine (Borrowdale upto Styhead):




Not the best selection but was going down so stopped when arms were feeling it/had to dab/thought might make a good pic of the down/waiting for walkers/etc