In a setup like this, I'd strongly recommend you look at various switching options like:
-- Befaco Muxlicer
-- Verbos Sequence Selector
-- Boss Bow 2
etc.
With some switching like that in your system, you can sequence your control signals of any kind, including sequencers, lfo, envelopes, etc. With not much HP and $ extra, you massively extend the depth of your control rig.
Also, with the goal "have a modular sequencer that can easily be adapted to use with a wide variety of other system" that begs the question -- what will it be linked to? Hence, any of a range of interface modules like Expert Sleepers or Boredbrain might get you fun extra linkages out (to PC, MIDI, etc.).
My net recommendations
-- think of how many pitched sequence lanes you need, how many perc sequence lanes you need, how many spare sequence lanes you need, and get a bit more than that, with maybe different sequencers handling pitched vs. perc
-- very much consider ergonimics and workflow in a sequencer, it matters a ton. I like Five12 Vector for pitched stuff and Tiptop ones for perc, because of all the knob per function, and how those really make more sense to my mind than others. IMO sequencers are a very personal thing so take some time to find ones that jive with you
-- totally include some switching in the rack and sequence control signals, it's the bees knees
-- with a good signal out box (Expert Sleepers) etc., you could use a rig like this to cover a majority of scoring needs
Good luck, enjoy!