ENIG or HASL for prototype with small pitch and expectation to need rework
I haven't noticed any particular problems "reworking" ENIG.  It's a right tools for the right job thing.  To pick off 0603 passives,  heated tweezer tips are best.

That said, I've rarely been in the situation of having to swap out R's and C's once I've gotten up to the point of printing a board.  Perhaps mounting your fine pitches on a breakout like from proto-advantage and using some other combination of prototyping techniques will let you figure this out in advance.

If you're talking about gearing up for a major production run, prototype it both ways (with and without your RC filters), or spend the engineering time in advance to figure out the values up front.  Perhaps you can leave the RC filters in the board, and a combination of Do Not Populate and zero ohm resistors can replace more expensive parts.  Or, you can print up some extra boards and populate them with different RC values until you have it right.