I also like the idea of the sign staying in NPS permanently. I do, however, have concerns about it's exact location in the square post-games. Once the PanAms have left Toronto, and the square isn't as busy as it currently is (and the security guards that I presume are there, are no longer present) then what is to stop some hooligan from tagging/spray painting the sign? What is to stop someone from taking a bat to the sign to destroy it? Pretty things in the public realm don't always stay pretty.
If we are to protect the sign from destruction, I feel that it needs to be removed from public access. Keep it visible, but out of reach.
The TORONTO sign cannot be painted over if it is tagged as that would block the LED lights shining through. Another presumption here (since I actually haven't seen the sign in person) is that it is made of fiberglass or some other plastic so that the light shines through. Those materials are easily broken.
By comparison, the iamsterdam sign doesn't have the same challenges as it is a piece of metal - not easy to break. If it gets tagged, you just re-paint it red as there are no internal lights.