It would be helpful if it kept growing. It would make it more viable to not start at a top 10 airport, and still be able to grow the airline to the same size as if the player started at one of the top 10 airports. Or even better do away with the limit all together.
For 99% of the players, 600 aircraft in bases is pretty much infinity, they never get there. It only limits a handful of players, playing in countries like Japan, China, Turkey, Mexico, Brazil - so doing away with the limit would not really change anything.
Players playing in the US / EU are not really affected. When starting at one of the huge airports in the US / EU, just filling the HQ may take 500-600 aircraft, and if they do, they will likely never approach (or need to approach) the base limit.
It would also make playing some countries (outside of USA, EU) more interesting. I am currently playing Turkey, at the max, while there are several airports in Turkey where no one is based, that are viable as bases....