Couple of myths around BIAB:
you can't do a step mash and cleaning the bag is a PITA
I always do a "step" mash, either a single infusion for UK and APA styles then ramp up to mashout
or a hochkurz mash at 62, 70, then mashout.
If the urn has a rack to keep the bag off the element, switch on full power then simply pump up and down with a paint stirrer for about five minutes between rests then re lag the urn.
Because you are going to heat up to boil anyway, then the various temperature ramps come "for free"
I don't use a bag, I gave up on them years ago and just use a circle of voile, lasts forever and there's no seams to weaken as well as hanging in a perfect teardrop shape. I throttle mine with a hangmans noose and use a double pulley off a skyhook.
To clean I take "bag" out to veg patch, undo noose, dump grain, flap flap flap the sheet then rinse or stuff into a 3L jug of perc and leave overnight then rinse. Takes less than two minutes.
Another quick step is, because I have a fairly new Hot water system, I use hot 55 degree tapwater that quickly heats up to strike temp. Manning Valley water uses chlorine gas so there's none of that remaining in the HWS.
Brew hours don't really bother me, being retired and empty nesters but if I really want to put the skates on I have an over the side immersion heater that makes short work of ramping and can crank out a double back to back batch in six hours.
My brew day is sub 4 hours as I can be doing cleanup etc while the boil is happening then the only real job is to hose out the urn afterwards.
Nothing against Grainfather by the way, sounds like a good system.