Bit by bit I am edging towards having a row specifically for percussion and I'm interested in what other people have for Mixing and Panning etc.
I'm currently a little bit short of Mixing capability having sold the Intellijel Mixup I had and I'm considering the next step in mixing.
At the moment I have:
Most of the percussion sources going via a WMD/SSF Quad Atten then into a Omsonic UPE (Universal Panning Expander) so I can tweak levels and Pan, I do like a bit of Reverb on Hatz so mostly send its outs separate to the UPE.
ModularGrid Rack

I fancy eventually upgrading the Mixing to a Befaco Hexmix with the STMix feeding it, though it would seem a waste to use up all the Hexmix channels with panning mono percussion sounds around so alongside the UPE I may get a Doepfer A-138s Mini Stereo Mixer.

But how would YOU do it??

I know the following is not about panning each percussion module, only the last option is about this I think (hexmix).
But you could use the stereo mixers to the Rosie Return stereo set.
Problem is that there are not many input channels in most mixers.
BTW dot / ll8 and Burst seems like nice combinations.

Already thought about the Befaco - Percall (on my wish list)?

MylarMelodies has a 'suggested systems' techno machine item on YT.
There he is using the Befaco Percall partly as mixer.
I am also changing very slowly evolving to a percussion rack, but my budget has been slashed this year (because I am in between jobs now).
My 'optimal' stereo set would be 4 Percalls to a Doepfer A138S stereo mixer, but that is very expensive.

(Title: How to make a TINY live techno modular synth in only 62HP.)

Another option (see my "end game" rack) :

Rosie + pico DSP
combined with 1 or more of the following:
Axys (on my wish list)
X-Pan (on my wish list)
I have a A-138N for each (Rosie) channel.
and a A-138S between the Pico DSP and the Rosie (stereo return input).
But I do not know if this would be possible with the hex modules.

another option :
MixZ tiptop (combined with TipTop drum modules) (on my wish list)
There it is possible to bus audio, instead of the need for cables.

Or going to 'real mixers' like HexMix / Hexpander / Hex VCA combinations. (also on my wish list)
like you said yourself.

DOT for Euclidean, LL8 for more of a fixed structure, I may end up using the Burst for more Twinkly synth bits rather than percussion.
Yeah I watched that Mylar YT, Percall does look lots of fun.
Rosie looks nice for a bit of end of line Reverb to tie things together.
MixZ sounds interesting, though would obviously couple best with load of other Tiptop modules.

Soundstage or a Jumble Henge or a Nearness plus some attenuators could do a lot of work for you. I have the first and the last and they're both really nice modules.

I also found the PanMix from Happy Nerding, maybe that is another option, that is 6 channels mixing, seems to suit the situation better.
(and my wish list is growing again, but I can delete some from the list maybe with this one).

All good suggestions, Soundstage is sounding good on @troux work, feels to open up the mix.

I've kinda had my eye on that PanMix cos you can CV it for Pan and Level @ThunderSound the ever-growing wishlist needs pruning regularly, its kinda slowly shrinking but shows growth-spurts after a prune, feeding it regularly with ModularGrid doesn't help!