First off I'm no modder so forgive my pics and explanations.
I thought adding the blade exchanger would be possible on the Signal as a few other had the same idea. I tried to fit an older style blade exchanger where the saw goes. First off the Signal pivots are much to short but the same diameter as the old surges. The Surge pivot would need to be shortened just a bit IMO.
As you can see in the pictures the BE would need to be trimmed as it hit the frame of the Signal and will not close. Its also wider than where the saw fit. <<< I wonder if it can be sanded down and fit >>>>
BE with saw or file would also be too long for the space.
Can it be done? I'm sure one of our resident modders could figure it out. I'm not going to tackle it myself as I just don't have the skills.