I think you will find adding a longer term MA very useful, almost essential, in highlighting the underlying trend and avoiding (some) false crossover type situations - I also do this (you can actually see that on that chart that I posted yesterday )
The only time that it can be frustrating is whenever the longer term trend is starting to fade and turn because, obviously, the follow-through on the short EMA’s will then inevitably be shrinking in the direction of that trend. So, as the main trend progresses through its natural cycle, beware of the waning phase…
This is one aspect of your trading that we have not looked at yet.
The selection of the most suitable pairs is something that is relevant to any trading method and can impact on its overall profitability without actually changing the method itself. As you have already noted, this 5-10ema crossover method is vulnerable on days where the market is stagnant. So therefore it is logical to always seek the pair that offers the most potential for moves - even if it is a cross pair rather than just a major.
One way of doing this is to also carry out a strong/weak currency analysis, which may help in identifying which pairs are currently offering the most potential in divergence.
You may like to look at this thread which seems to produce some good advice regarding currency pairs and see how trading your method using its SW pairs compares with your own standard pairs that you mentioned. For example, it may have produced better, more probable, moves by trading the GBPJPY rather than USDJPY - the issue here is: does this add-on analysis give you an extra edge?. Personally, I think so.
This thread is not a trading method as such. It just concentrates on highlighting how the major currencies are currently moving. Any trader can use this data to their advantage in whatever method or style they prefer.