I'm not so sure about mixing them. My gut tells me that the resistance of the nickel might be too low for an outer wire and kanthal obviously will not work with temp control. I'm just not sure if the coil will fire properly in standard VW mode. I have seen people successfully using all-nickel claptons with TC effectively. I'm just really not sure about combining the two. A nickel-core clapton with kanthal wrapped around it may work with temp control, but it could be wonky because of how the kanthal can ever so slightly alter the connection to the core, and thus the resistance it reads out to at such and such temp.
I'll tell you the same thing I tell most people looking to try claptons. Get yourself some 28g, 26g, and 24g for cores - 34g, 36g and 38g for outer wraps. Stick with kanthal and/or nichrome. Those two can be mixed, if you want (especially on a regulated device.) Just start playing with different combinations of those gauges before you start tackling unconventional combinations of wire.
The basic principal for a smooth-vaping clapton with plenty of flavor/vapor and little ramp-up is a core of moderate thickness (big enough to heat up the outer wire, but not so big that the wraps bog it down) and very fine outer wire to create finer gaps without adding too much mass (thicker outer wire retains more heat and makes for a slower, harsher, and much hotter clapton.)
You could try a 28/24 clapton. Probably not ideal, but certainly vapable. I would recommend keeping the resistance/wrap count pretty low, as even something as small as 4-5 wraps @ 3mm is going to be pretty hefty and power-hungry. It might perform pretty well on the Sig 150w, though.
