>>44914156x6 TLRs are a lot smaller than you'd think.
A folder is probably always going to win on compactness, but zone focussing and composing with the brilliant finder on my Ikon 515/2 sucks. My Microcord (Rolleiflex copy for all intents and purposes iirc) is smaller volume wise than my 35mm SLRs.
>>4491421I understand the packing purposes issue but personally when I've travelled with my folder I always brought a 35mm SLR anyway because I knew the folder was so limiting.
There are a few folding rangefinders, like the Mamiya Six, Voigtlander and Zeiss made them also. You could always get a hotshoe rangefinder and mount it to your folder.
tl;dr Like you say if you bring the folder you will want a 35mm also, so the TLR is there if you want to replace both I suppose. Unless your folder has a rangefinder already in which case I think wanting anything further is GAS.