It's not particularly hard to start playing acoustic after you've been playing electric.  Your analogy comparing it to a similar change with guitar is actually pretty close.

The basics don't change.  But the two instruments do have some differences that you'll find in fine points like how much pressure or speed to get a certain timbre/tone to the note, and how some techniques physically feel can be slightly different.  But it is close enough that it is definitely not like starting all over from scratch.  Most of what you learn on either works fine on both, with maybe some minor adjustment.

A bit of advice, though.. When you do add acoustic to your playing, try and get an acoustic where elements of setup like the curve of the bridge and the feel of the neck are similar to your electric.  It makes switching back and forth between the two easier.

My first acoustic had some differences like the neck being a little thinner than my electric (distance between back of neck and top of fingerboard) and the bridge curve being slightly different.  It all worked, but made it feel enough different that switching between the two took some conscious adjustment at first, since they just didn't feel the same.  My current acoustic is more similar to my electric in those particulars, and I don't really even think about it when switching between back and forth between acoustic and electric.  Sure, there are differences, but they are close enough.

The biggest difference is sound and feel, though, and I find some songs just work better on one than the other, and I'll get different ideas on electric and acoustic.  But that is very similar to switching back and forth between electric and acoustic guitar.  A matter of taste and of which instrument feels more appropriate to a given piece.