Okay, so I have a massive multi-fx plugin - there are 6 slots in it, and each slot can load any of the FX that ship with the plugin.
There are 133 FX.....
Yep, thats not a typo ... 133 FX.
Any of these can be loaded into one of 6 Hardcoded FX "slots", there are C++ FX, Scriptnode FX and Faust FX all in there....
So now I'd like my plugin to report to the DAW some consistent delay time...
So the plan is, nothing special here, to have a variable delay at the end of the chain....whos value can max out at the worst case scenario (6 copies of the worst "performing" FX loaded across all slots in the plugin), and to calculate every time a new FX is loaded what the current delay is - and add "make-up delay" to get us back to this worst case scenario - and thus always report this worst case to the DAW.
Now I realise that some of the actual delay any given FX induces may well be changable based on the params the FX are set at, the sample rate being used or even the type of content arriving at the plugin.... Im going to live with this inaccuracy.
Heres the plugin layout - its pretty simple:

So, to the question:
What currently the best way to measure delay induced by any given FX?