I once saw an automotive board where they had used loads of MLCC instead of El caps. They had to use the ones that are "kind of on stilts" as otherwise they got too much problems with cracking if ever the PCB was roughly handled. (which it often was when eg mech engs took the board to do measurements on, etc etc) Ive forgotten what you call them now, its like a ceramic cap but its on like a platform, so it is spared flexion stress.
Other way is to use radial ceramics of course. Or ceramics on "plug-in" platform PCBs, which may (or may not) have been what Easy Peasy was referring to?
Shame that you cant use supercaps. I dont think all are as bad as el caps.
With multiple interleaved phases you can very heavily reduce ripple as you know.
One alternative is to just have supercaps, but make the bank easily remove-and-replace-able, so when it fails, you can take it out...or just replace it anyway after a year or so.
Woudl have thought modern tantalum capacitors could be OK too, as they are not as bad as el caps, and the newer ones dont have surge current problems like the older types.
Wet electro , AYK, is the king of handling high one-off surge currents.