That all just sounds like a lot of work and not to mention heavy.. There have been almost as many fillet threads on here as there have been Fox .35 burp threads. Just make for a good , close fit between the fuselage and wing, (fill in any large gaps with glued in strips of balsa) then apply some Super-Fil, or epoxy/micro balloons and smooth those out, then lightly sand those, then apply the same sealer/filler that you apply to the rest of the airplane. If the stuff you are calling "soft filler" is anything like vinyl spackling compound you will have issues with paint lifting off. Sealing with CA glue will only show you how much that can raise up the surface when it kicks off and will not sand very easy at all, after you thought you had just finished with sanding. Do some fiddling with the search function and I'm sure you can call up a couple of hours of reading.
  Type at you later,
  Dan McEntee

The soft filler is Elmer's Wood filler, we have used this on many ships it grips and sands much better than spackle. Left on just enough thickness to fill in the little groves left after sanding the epoxy. A friend use to use it on the whole ship like a fill coat then sand it almost all off, never lifted. I did use the balsa strips to fill the initial gap and get it close, then applied the epoxy, was about 8 grams total mix used about 6 grams. Joint is strong and smooth ready for finish. Will likely give it a wipe with CA then clear dope  a couple coats then color.

Best,   DennisT