about the deadline I would prefer "when first doubles match start" if this is okay for manager.
I dont like it, to use the partners picks if someone is late. It's really their fault.
what about alternate teams (LL like in TT)
Of course, that is what I meant 'when first doubles match start' which means in my example when "Nestor/Zimonjic match starts". But, we never know .. Since Nadal/Federer may not be played because of w.o., in theory, to secure things, all DTT players should send their picks between 14:00 CET. So, if all picks are there at 14:00 CET, DTT manager should be allowed to publish diffs at that time if this is more convenient for him.
Regarding your remark about "it is their fault", I agree. But, for instance, I am out this week in Doubles because of diego36arg not sending picks even if we were +3 after day 1. And diego sent me his picks 2 hours after deadline. Of course, this should be exceptional (allowed only once in the tournament, and you could have penalties for that, eg. if you are tied, this should be first TB criterion before SRs) but it would help to keep the fun and be more tolerant with a player not sending picks (and not penalizing too much the partner). When I was in opposite situation, it is not fun for me to win by wo because one guy of opponent team did not send picks.
Of course, if you have alternate teams sending both picks, they should replace the team who has sent 0 or 1 pick. So, this "exceptional" rule does not apply on day 1 of first round of tournament (except if there is no alternate).