indeed, this is how I use my Hermod too 
though feels a bit ‘overkill’ … but I do enjoy having a separate sequencer in the rack ‘just in case’ 
(you can never have enough modulation sources!) (*)
BUT, the difference too my suggestion for an expander is:
not going via midi
this means higher resolution, and also higher data throughput … these are the primary advantages of CV vs Midi
also as an expander, the hapax would see this module as extra CV/gate channels (in and out)… rather than as midi channels, as it does with the Hermod.
the ‘issue’ I see is, its a pretty niche market…
not only is it only for Hapax users, but the subset that are into eurorack and that need more cv/gate channels.
this was why I suggest it could also support midi, so it could be useable with other sequencers etc (sure, not getting the advantage of direct CV,as above)) thus extending its reach a bit.
there aren’t that many midi->cv, cv->midi modules with a few more channels, basically the Shuttle Control/FH2/Poly 2/Hermod… (plus a couple more im sure)
anyway, I think its unlikely to happen, but we can dream
(*) I have talked to Squarp about the idea that perhaps Hermod could perhaps have some features to explicitly support better Pyramid/Hapax integration.
as a company if you have a range of products, of course, they need to work standalone perfectly, but adding ‘bonuses’ for using combos of your products creates benefits for staying ‘in brand’…
we see this in other industries, e.g. look at things like Sony TVs.
of course, the ‘protocol’ you use to to this can be open/documented (e.g. documented sysex) , to avoid the inevitable accusations of ‘lock in’.
so would look rather similar to the pyramidi of the pyramid.
