The C15 is stable, has an open cockpit for either one or two users, and is reasonably seaworthy. I'd be leery of taking one out in the open ocean, mostly due to the big open cockpit and low freeboard.

A number of folks have added sail rigs to the Chuckanut 15, and she performs about as expected for a boat you can't hike out on. She'd be a little more reassuring with outriggers, and you'd be able to push her harder, as well. To a point - she isn't really engineered as a sailing canoe, so I'd limit her to lighter air.

Just off the top of my head, and not taking into account much of your preferences, mods I'd make to the C15 would merely include:
Beefing up the scantlings of the gunwales, carlins and keel, and reinforcing the second frame.
Modifying the aft stem to better accept rudder hardware. [I'd use a tiller yoke, with a long push/pull extension, rather than foot pedals, so as to allow precise steering from anywhere in the cockpit.]

Modifying the coamings to accept a Michael Storer designed "drop-in sailing rig." It's a sail/mast partner/leeboard combination one can add to most canoes and/or open kayaks.
http://www.storerboatplans.com/Canoebits/KayakRig.html

I'd pair that with small outriggers connected by a single aka, likely attached to the aft portion of the drop-in rig.
This would give one enough stability for enjoyable sailing, without teasing you into potentially over-stressing the whole system.

Simple and easy to rig and de-rig.

On another note, if you want a seaworthy outrigger sailing canoe, I have recently completed a small SOF Perahu Katir - a type of Jukung from NE Java. I'm still in the sea trials stage, but so far, so good. She is meant from the outset to be a sailing canoe, but she does also paddle great. 17' by 22", about 70lbs, with 73sq ft of sail area. I hope to have plans available for her in the Fall.

Here's a pic (and those outriggers are big bamboo, not pvc).

Dave Gentry
www.GentryCustomBoats.com