I´m against getting rid of it.
Unlocked sliders generaly lead to a distinctive rift between naval and landnations which historicaly never happened this way. Also it thus limits the fun of the game.
Rarely do you, for example, see a navaly active France if sliders are unlocked. Nor Spain for that matter.
On the other extreme you have english, portuguese and dutch armies which aren´t worth a damn until the late game which is equaly unrealistic and needlessly constraining.
With locked sliders everything get´s more complex and interesting for then you normaly have far more powers building serious navies and using them.
Take "Defeat Before Dismemberment" as an example of this. This campaign may have been intense and ruthless but it was by no means boring. I say this was due to a considerable part to the locked sliders. Almost every nation was navaly active and had holdings in overseas. Even Austria though they soon lost all colonies again....which was, of course, most historical indeed.
Please do not remove this most vital of rules from this campaign.