Sweater dilemma

This is a current picture of my Lofoten sleeve, taken after Colloquium the Thursday before last.  The measurement that prompted my dilemma is the length: 18.5" from the purl turning row, with four more increase rounds to go before I get to the stitch count for the top of the sleeve for the 40" size.  The schematic gives some ridiculously short length for the sleeve.  I don't remember exactly what it is, but under 17".  I am at least 5'10".  I cannot wear a 17" long sleeve, no matter how much ease there is in the body (the pattern suggests at least 4" of ease).

This discovery, Thursday morning just as I was trying to grab my knitting and get out the door to go to work, prompted me to think about my gauge, and to calculate out the intended gauge of the pattern.  I really think it's ridiculous that this pattern (which is not free!) only specifies the gauge for the colorwork sections, even though the plain stockinette takes up WAY more of the sweater.  But I'm a mathematician, so I can figure these things out.  The gauge for the stockinette is supposed to be the same as the gauge for the colorwork (WHY?  doesn't the pattern writer realize that people are likely to get wildly different gauges for dense stranded colorwork and plain stockinette?) - 25 sts/4".  I got stitch gauge easily for the colorwork bracelet, so I figured I was fine.  But my stitch gauge in the stockinette portion of the sleeve is 21.5 sts/4".

I did a little bit more arithmetic, and even if I knit the smallest size (36"), I now expect my sweater to come out a bit more than 40" around.  Good thing I'm not twig-skinny!  So my plan now is to start the body using the stitch counts for the 36" size.  I'm not sure yet what to do about the sleeve.  I might end up frogging it and starting over, or I might just frog the stockinette part, or I might make it work to use what I've already knit, depending on what the stitch count is supposed to be at the end of the sleeve.  I'm trying to tell myself that this is why I started with a sleeve - so it can be a swatch that might just end up being part of the sweater.