The C-41 developer was designed to give parallel curves at 100 degrees F and nowhere else. If lower temperature developers could be used for C-41 and give said curves, then Kodak and Fuji would have done so, but they haven't. Other manufacturers in the past have made developers that used low temperatures, but if they had been successful they would likely still be around, but they're not. The results may look acceptable to you, but may not be to someone else. Users are urged to compare print results side by side between film developed at low temps and 100 degrees F (a gray scale or skin tones are preferable) before they decide to stick with a low temp process.
I've never tried it as I use a Jobo for C-41 at 38 degrees so I can't comment on the results. Since the OP was looking for ideas on processing without temperature control I figured I would throw that one out there for consideration, is all.