It's actually better to put it on someone like Mash (0 cost Servant) in your party instead because during story quests, you may get the option to use a story related Support unit which gives 200 FP, having it equipped in your party means you'll be getting 275 instead, which is nice. People should be using this method instead of slightly gimping their best Support with a mostly useless CE. You'll get +75 from everything that way. You might be wasting someone's attack on a unit that could've died if your Support just had that little bit of extra attack or command card boost.
I've set my level 42 Archer w/ Kaleidoscope (80% NP charge at start) as my All Class Support for today's EXP daily, use him if you want to clear out/weaken a group quickly. Hopefully more people learn that you can switch classes at the top bar to see all of a person's Support units so I don't have to do this for each daily. Waver's probably going to go back to that slot afterwards.
I also have 3 slots available on my friend list right now, check out the google doc in the OP if you want to add me. Whenever they give out that 4* Servant, I'll have Heracles, and that should give me a pretty well-rounded Support crew rolling.
EDIT: Make sure to add your name to the list so I don't assume you're some random stranger. It also helps if you don't have a mostly empty Support cast with just a Mash at level 1. Especially if you're just lurking. -_-