Yes it is.
Coil splitter is for humbuckers, you would be doing the opposite of a coil split, it would be a coil join.
The diagram below is how I rigged my old jag so that when both p/ups are in the off position on the lead circuit, both p/ups will be on in series, effectively making one big humbucker. You will get to keep the strangle switch as a strangle switch this way and the only option you lose is to turn off both the p/ups at once, although I don't know why you would want to do this anyway when you could just turn down the volume on your guitar to achieve the same effect.
