Here's my thoughts, take them for what they're worth

1) Plans build vs kit built. I can't tell you how many times people ask/infer my Cozy is a kit build. They're dumbfounded that I'm building a 200 MPH plane off a set of sketches that were sketched pre AutoCAD. A tub of epoxy, blocks of foam, and rolls of fiberglass. Nothing is pre-punched or pre-formed.
2) Cozy is the only plans built canard you can actually buy now. RAF bowed out of the plans business for various and sundry reasons. Aerocad may still offer plans, and I think Velocity offers a hybrid plans/kit as well as a kit.
3) Liability. Kit built, metal anyway, has everything more/less pre-made. Simple matter of inserting tab A into slot B, and squishing a rivet. And a good/bad rivet job can be checked with a gauge. Compare this to a plans built canard: "make it look like the picture". Tons of variables in the latter, and hard for the designer to prove it wasn't made just like the picture. We live in a litigious society.
4) Support. Lots of forums and mailing lists out there for Canardians (not to be confused with Canadians

). This may be a disadvantage for a new/potential canard builder, they may expect all support to be in one place like the Vans or Velocity websites. I know I get answers to my Cozy questions quickly, often w/in the hour. The rest I knuckle down and find the answer myself. There is a wee bit of hand-holding for new canard builders, but it's not near as much as I've seen for other amateur built planes.
5) Sex appeal (and/or babe magnets). Canards. Nuf said.
6) Unsupported. There are plans out there for building a tandem canard. Spend a day, or more, Googling for Open EZ plans. Suspect you could also build a Veri-Eze if you wanted to, but it'd be a chore making some of the special fittings (wing attach) yourself.
7) New design. I would very much like to see plans for a stretch Cozy MK-IV. A bit wider, and a foot or more longer, to make a real comfortable four place cross country machine. The market just doesn't seem to be there. As to 'reinventing' the tandem canard, see the bullets above.
If you have your heart set on a LongEz type, poke around the interweb. You will find the support you're looking for, it just won't be in one place.
Attend one of the canard fly-in's! There are many, but spread out across several website's

Rough River is the premier one (roughriver.org) at 2I3 west of Ft. Knox, KY. RoughRiver is
total canard immersion. The West Coast event is "Canards West" in Columbia, CA. Expect to see rocket scientists there. Then there's Kanab, SnF, Copperstate, Burrall Saunders gig, OSH, ...
Rick