What about Red Screes from Kirkstone? Nab Scar? Or up to the far end of Scandale and up Red Screes that way?
Would all seem to me to be steep enough (without being too severe) to rack up the climb...
Nab Scar steps seems a good option - no significant level sections, good traction almost all the way - I will give this route a go. Have had three goes is three days so far, two on Wansfell Pike, one on Loughrigg.
The world record for a vertical kilometre is astonishing.