I am lost to why you think weekly macd crossover are not a good indicator of a buy signal.. just looking at the charts.. makes me think that you're not 100% serious with that statement. In regards to bitcoin trading.
Because it has a poor historical performance as far as I see (have you looked at the last signals it gave?), and it's been my experience with the daily as well. Much more important than crossovers are the establishment and break of the zero and signal line as support and resistance.
It's like saying the people who bought at 266, are going to regret avg down on the rebound from 80ish last november. If you thought bitcoin was going to 0 .. then sure..averaging down makes zero sense.
No, but it can go a lot lower than you imagine (will you have sufficient size to buy with to equal the others if it falls again and again and again?) and stay there for longer than you can imagine. Averaging is viable if you only want exposure and determine beforehand that this will be your strategy for entry, but then it should be bound to progressing time, and not decreasing price.