I did similar cases a few times.
I would add some good adtenuverter modules, like:
Befaco Atte, Black Noise Goma II, Rides in the storm QUA
or for 1u: Befaco 1u Motion MTR, inntellijell quadratt etc
Other option coulde be to add a Axon 2 expander besides your Pamelas Workout and discard ochd, tilt - to do all modulation just with Pams. A mixer module in the 1u would be useful to mix cvs but if you just use Pams + Axon 2 - you can mix and atenuate your modulation just in pams.
On the other hand ochd works well with morpagene and mimeophone
a Cara marbles clone works well in small cases
a Gliss 1u could be fun to record custom lfos and more stuff.
a small compressor like WMD mscl could be useful 4 hp
BAStL Ikarie is a good choice as a small filter with stereo spread and some gain. 8 hp
Rackbrute 6u is nice but then it will be harder to transport and it will be more as just a small effect rack.
Go for the Rackbrute if you want to build a whole ambient setup, with own voices, more complex modulation etc
watch out for some noise sources.
My secret weapon of choice is: SGR1806-20 kNoB technology but there are smaller alternatives.
A Benjolin could also be a good fit, like Benjolin V2. chaotic random + osc + filter.
Another idea could also to drop it all and to just get a "Befaco Oneiroi" for a pod or as standalone. = intant ambient similar to such a effect case - or maybe just Oneiroi + Pams
I would go definetly a whole different route with a Rackbrute 6u as with a palette case.
Greetings
Chris