If that were true, then Plarium wouldn't have any problem with changing it from a-coins to credit WITHOUT changing anything with the current credit system.
You can't say that the current system of Implant replacement is set for careful planning when you can only store 5 mechs. It doesn't make sense. I can "carefully plan" for 5 mechs for Arena.. but that setup will not work for 2v2 or Capture Point. And you know that.
Instead of charging a-coins just to swap out setups, a more fair system would be either
1) Change the currency to swap out Implants. Make it cost credits instead of a-coin. (again, WITHOUT changing the current credit system)
2) Give us the ability to store 10 or 15 configured mechs. At this time, we can only save the configs for up to 5 mechs. So your "careful planning" can not even be applied when by the flaw of the game design, the player MUST reconfigure the mechs every time depending on the game being played (arena, 2v2, capture point)