The ballot layout issues would still be there. If the voter is to be able to rank all candidates, then you need to have each candidate's name on the ballot.
It would still save time, since you could sort the ballots into piles for each party. Also, coalition negotiations could start once the party votes were counted and the seats allocated between the parties. The PR-STV part could take longer than normal. Also, the party votes part would be precinct summable, even if the PR-STV stage isn't. Another option is the "candidate-list" system where each candidate submits a list and you vote for 1 list. ---- Election-Methods mailing list - see http://electorama.com/em for list info
