Plus they've been integrating Sakamoto Kouichi into the direction more in recent years. Didn't he say he "slipped in references for PR fans" into Gokaiger a few times?
I'd say the fact that it's spelled モーフィン means it has to be a reference. Japanese otherwise spell the word (morphing) モーフィング, and their dictionaries only include the recent, technical definition of "morphing," "to transform (an image) by computer."
If you search for モーフィン on Google, what you get are links about MMPR. At least, after you eliminate all references to morphine.
(Surely no one is so in-denial about Japan caring about PR they're going to convince themselves that it's the "morphine brace"... right?)
I don't think the others are necessarily references "for the fans" -- it might just be them re-using ideas they saw (and Sakamoto directed, let's not forget) on PR and thought were neat, or it might be a coincidence. But I have a pretty hard time seeing any use of モーフィン not being a deliberate PR reference. MMPR may not be huge in Japan, but it was shown over there, and people would at least know of the name.