Hey DjC, the whole A/D D/A thing is one of my major bug bares and I barked on about here for a long time. I'm an analogue die hard and paid my dues in the land of tape. Feel free to email me if you want to have that conversation.
There are a bunch of posts that MikeB and I did when we tested using his (beloved) GMaj2 mixed in in parallel to preserve the MP-1 analogue signal path all the way to the speakers and then chaining through it. This came off the back of me getting a TC MOne XL reverb and reading the schematic. The first thing TCs (and many other units) do at their inputs is A/D the signal (
no more analogue MP-1 dry signal). We proved that preserving the analogue dry signal (as you do with an analogue desk (which is how I do it) or with an older school Fx eg Quadverb? Intelliflex) does sound better (I spose you might describe it is as less colour). Then SC pointed out that sure it may be a little better but is it worth it given how you can use the midi continuous control options in the GMaj2 and it still sounds killer... So very much up to the individual how "picky" you want to be. And Mike has gone back to chaining through his GMaj2 to get the other benefits, mainly stereo mater vol control via midi expression pedal (which I don't need as it's built into my MP-2).
Of note, all this is running stereo. To get the best out of these multi Fx devices they sound allot better in stereo, as does the MP-1/2 (or you miss half of what they do or are supposed to sound like).
On the subject of colour, all units have a sound, some are more transparent (and typically cost (allot) more).
If you are that pedantic about colour (as am I it seems) and want to add some Fx, then IMO the beast way to realise your aim/goal is to use a reasonably high quality "analogue" mixer and run your rig "IN STEREO" just like a PA system. Use the Fx send to feed Fx units, return them down input channels (or returns) set 100% wet, get the gains set right and blend it to taste. Now I've done it this way from the get go (I'm an audio engineer, it's the easiest way to do it (for me)). For Fx, buy really high quality units (hey I'd like to have a Lexicon Lark 224X reverb
$$$s) that "you" like their sound.