Judging accidental/deliberate is always going to be a judgement call by the ref, nothing you can really do about that. Same with the vast majority of similar judgement calls you get in a game.
As for the advantage, well, you are most definitely better off if you do it in the dying moments, during early open play is more debatable, i'll concede. That said, punishing a goal line handball by awarding the goal and sending off would certainly make players think twice about doing it.
Ultimately though, the Ghana - Uruguay match just demonstrated there was a 'loophole' if you will, in the current rules.
If they had played that sequence fairly, they were out, cup over for them.
Breaking the rules though, puts them at a clear advantage.
- If they don't get caught, awesome, blocked the goal and no penalty for it at all.
- If they do get caught, they go a man down for a bit and have a chance that the penalty won't get converted into the sure fire goal they just stopped happening. Given the pressure on such a kick too, the odds must be pretty good on the miss as well. Crucially though, they are not out, even if they have to play extra time with 10 men, it's better than being out. Even if they have to play the next game without a key defender it's better than being out.
As it happens, Uruguay did benefit and eventually went through.
Even removed from the Ghana Uruguay setting, can you see what I am getting at with this? In that situation, at the end of the game, there is absolutely no reason not to cheat other than the players own morals, quite the opposite, you are effectively rewarded if you DO cheat. I think that's a flaw in the rules.