I wanted to make sure I had permission to post the email response I got from Harman/Revel support. Now that I got the green light, here it is:
"The protective bars for the tweeters are both for protection and the finished speaker is optimized in terms of sound quality with these in use. All of our transducers are conceived and designed by the Harman Engineering team and built to those specifications.
Unfortunately the removal of the protective bars, and use of unauthorized parts will consequently void any implied warranties or certification of performance. Furthermore, our specifications as well as technical data are extended to the complete finished speaker."