Sure, a switch rod will give you versatility. But there will be a trade-off for sure. You'll need different lines for the type of casting you want to do. For example, you won't be able to efficiently (if at all) cast a spey line/skagit head overhead (like a one-hander), and the same will go trying to spey cast a WF line. Even if you do have a WF line suited for single-handed casting, the switch rod will be much heavier and less pleasant to cast than a single-handed rod. So if you want to use the switch rod to do the work of both a single and double handed rod, be prepared to carry two lines (extra spool or reel) with you.
I personally love my switch rod, but I primarily only use it for two-handed casting as my single handers are much lighter and more pleasant to use for single handed casting. In fact, there are times when I bring both my switch rod and a single handed rod to the river.
As for using the switch rod on a centrepin, sure - you could do it. Again, probably not as efficient with a proper centrepin rod, but it is doable.
So, I guess you need to decide if you want versatility over efficiency.
Edit - just saw that Ralph replied. Agree with his thoughts as well.