I've had some luck with using tape to pull decals off, even those that have been sealed with a flat coat... The trick is to apply the tape to the decals and not the finish... You can't just lay the tape down over the decal and pull it off... Wrap it (Masking tape, BTW, not the low-tack modeling masking tape either) around your finger-tip for larger areas, then wrap it around smalle tools, like the end of a brush for pulling up bit's & pieces. You'll likely still have to go in VERY gently with a NEW razor knife-blade too.. Sometimes you can "shave" a decal off...
Better test it on a hangar queen if you're going for contest builds though...
I'd also forego using Future to gloss coat (or any other gloss coat for that matter) for application if this's your plan... A satin/semi-gloss decal application coat is smooth enough, and wouldn't be damaged as easily... Just be sure to check for silvering and fix it, and also trim as close as you can to decal ink, leaving as little clear carrier film as humanly possible, even if you have to cut the decals apart here & there... A new blade on a mirror or a piece of glass is the best surface for this operation, NOT a scissors or blade against a cutting mat.