Couple comments/idea.
On Funhouse, doesn't the board on the front left of the cabinet have a 12v tap? I understand taking stress off the driver board but to me if the power is there that's an ideal power tap and less mess.
Secondly, the one thing I wish I had done differently when I installed a shaker in my LOTR (pinballlife kit) was to put it in the middle of the cabinet instead of the front left. Physics ... duh. It stands to reason reverberation will occur more on the side/area it's mounted on. I think on most pins, there's likely room enough between the speaker and the cross brace. Add a couple wire loops to clean it up and BAM!
When funds free up definently will add one to my TAF AND FH. I think about the current machines with a shaker installed from factory and how they interact. Used tastefully and sparingly. Both very important. I think on TAF, the topper GI (used sparingly) bookcase motor (some what sparingly), train target (most people go for ramp so used sparingly). Thing is used quite a bit and honestly I think would get annoying real quick especially for the length of time it runs. Maybe the vault switch? Would love to hear others ideas on physical placement and incorporating.