Here's another (maybe crazy) idea: If we know for sure that Serbia #3 is playing Friday, why not slot Milos in @#2. ie.
day 1: Frank or (Vasek) vs. Tipsy / Milos vs. Serbia #3
day 2: dubs
day 3: (Frank) or Vasek vs. Djoker / Milos vs. Tipsy
Basically the only real difference here is that the key #5 rubber (Vasek vs. Tipsy) gets moved to rubber #1 (and now Vasek doesn't have the pressure .. he knows we have 3 other winnable rubbers coming up) and the key rubber #5, we have Milos vs. Tipsy rather than Vasek ... I know this is kind of unconventional (maybe even gamesmanship?), but objectively if winning the SF is our #1 priority, we'd have to win 3 out of 4 matches now & this gives us our best shot (ie. why waste Milos against Djoker's only appearance?).
we can't do that though. You nominate your 2 singles players and the higher ranked on plays the lower ranked opponent on Friday, and plays first Sunday. The only way around this is if your player is legimately hurt and he cannot play the remainder of the tie someone can sub in for the Friday.
The only circumstance where Milos gets to play the final rubber is if he subs in for an injured player, and I'm fairly sure we're going to nominate Milos to play and not be a sub for a fake injury we won't get away with.
If for whatever reason Nole doesn't play(I think he will, he played injured last year(?) because he figured him injured was better than Troicki, I think him tired is better than Lajovic) then it should be Milos/Lajovic, Vasek/Tipsy on day 1, and Milos/Tipsy, Vasek/Nole on day 3(in that order Sunday)
also if there was some theoretical way we could sub Milos in as our #2 the day 1 matches wouldn't look like that. It'd be our 1(Vasek) v. Their 2(Lajovic) and our 2(Milos) v. their 1(Tipsy), and then Nole would sub in for Lajovic on the final day and play Milos not Vasek