I assume that by Jobo you mean a Jobo rotary processor. If so….
The Jobo will half your chemistry bill, which must be worth it if you are using the rather expensive Jessop kit. If you have got the Jobo, why not use it ?
I haven't seen any low temperature kits, but then, with the Jobo CPE2, I don't need one. I suspect that if Tetinal (http://www.tetenal.com) doesn't do one, the demand for such a thing just is not there.
Short developing times are not a problem, as the film and chemicals are made for rapid processing in a commercial environment. However, if you tend to slightly over process, you will get more contrast and a little more colour saturation, both of which could be countered by shooting on Reala, or printing on a “portrait paper”.
If you are printing your own RA4 (or scanning for digital), you have some scope for experimentation with time/temperature, as colour shifts can, to a certain extent, be corrected.
For what its worth, I make up my own C41 chemistry using the recipe given in the Rayco handbook (http://www.rayco-chemicals.co.uk). This has a recommended process time of 5 minutes at 35 degrees when hand processing. I’m at work, so I can’t give you agitation details, but I think they are essentially the same as for most types of B/W film. Their gloop uses a standard “all in one” colour developer ( either CD3 or CD4 – can’t remember which ), so the active ingredient should be equivalent in potency to that in premixed developers, so this time/aggitation regime may work for you. Anyway, it’s a start !
By the way, with the CPE, I run at 36-37 degrees( depending on the ambient temperature), which allows for the inevitable drop in temperature, even with a water bath. I think Jobo mention this technique on their website. (http://www.jobo-usa.com).
I started this chemical mixing madness when work commitments meant that my chemicals were going off faster than I could use them. Unfortunately, such an approach requires an investment in hardware (scales, pH meter) although these can be offset by lower chemistry costs, especially when compared to low volume “consumer” kits like that sold by Jessops. The Rayco recipe has always given me good results, although I print my own RA4, so I’m probably getting away with a lot ! Can’t say that I would recommend this approach to anyone who is not already chemically insane !