The loops were removed as many people who have larger racks (like you with several pieces dedicated to individual functions) have post effects run in parallel with the output of the preamp - thus preserving the unaltered tone and mixing in the effects. Some people run larger W/D/W (wet dry wet) systems and have no post effects in the signal path, and the dry signal- unaltered sound from an amp head or pre/power amp setup are sent to a cab with that miked, sending its post power amp signal to the processors which is then sent to its own amp (usually in stereo - but can also be mono) and its own cab(s).
When I had my large rack setup (I had 3 preamps and 4 processors) everything was run parallel - and had a mixer in the system with the preamps hitting the mixer with no post effects and each processor hitting the mixer - so no processor saw anything other than the original signal from the preamps, all sent to a pair of 4X12's in stereo. There are a few things that do not work well with parallel post effects (mainly chours, tremelo, a bbe and some other effects), and in the case of that type of processing you would just run the pre into the processor.
Most processors that are made today do alter the tone quite a bit due to the analog to digital conversion (some are much better than others), and the only loop that helps to keep the tone is a parallel loop. The quality of the loop also has a big effect on how well the processors sound. By not having a loop in the preamp, as it is argued by most, helps to make the pre sound better due to less in the circuit. This also allows the end user to choose the type of mixer (loop for lack of a better term) that fits their system.
The single channel Egnater mods sound great in the Randall (I have a RM100 head and combo, a RM4, a M4 and just sold a MOD100) so I use a mix of randall and egnater single in my setups - each have their own distinct sound so they do affect the tone, but not in a bad way. No matter which way you go the tone is great, I've just found for myself I like the single channel setup better.
As to the Ground control or all access - they work great. I have a ground control (old) and a GC Pro - along with an axess MC5 and have no problems with switching any of my rigs.