Are you adverse to 3rd party added options?
Bidule: Object oriented hosting within a host. All sorts of routing, building, monitoring, and transformation tools built in. The free demo is ReWire and stand alone only (Cubase supports ReWire), but the paid variant can be run as VST in inserts or VSTi in the rack or instrument tracks.
With bidule, ideally you’d host your complex effect/sub-mixing chains in a single instance of Bidule. It includes mixing bidules and more. With the VST plugin variant, anything you like hosted in a bidule plugin instance can also be assigned VST lane, MIDI, or OSC controls for high level automation. With the ReWire approach I think you might have to do any automation to controls of hosted effects via MIDI track.
A catch with using bidule would be that those ‘Cubase Only’ insert effects won’t be available from inside Bidule. You’d have to work with alternate plugins, or, get creative with dispersing bidule instances ‘between’ the Steinberg ones in quad or surround sound busses in a series and just using bidule to ‘reroute/sub-mix’ some things.
If you’re on Windows: ASIO Link Pro: A free, high quality, supposedly zero extra latency multi-client ASIO bridge that allows all sorts of interesting audio routing at the ASIO bridge Level. Route among ASIO and WDM apps, can also loop Cubase outputs back into the mix, double signals, etc. It can also optionally stream to other instances of ASIO Link Pro (locally or over a LAN/WAN).
The Bidule option should be pretty future proof as long as Cubase supports VST and/or ReWire.
The ASIO Link option works great now and in my experience adds unparalleled routing freedom to an ASIO based DAW workstation. The catch might be that it’s no longer supported software…someday it might stop working as OSes evolve and change.