3holelover
In response to your questions:
Why would I need any high lift devices in cruise?
You don't. In cruise, the wing provides plenty of lift. In fact, wing area is often larger than required for optimum lift to drag ratios because it may be sized to perform other tasks such as to carry enough fuel for the mission, provide for airplane growth etc.
Takeoff and landing is another story though. There you need the "clever bits" i.e. the high lift devices. The success of jet transports is due in no small part to being able to minimize wing area for cruise while using efficient high devices to have acceptable takeoff and landing speeds.
This is where a canard has a problem. Look at your comment to Squawk 8888. The canard will stall before the wing on a canard configuration, because the wing is operating in the downwash field of the canard. At stall, the canard angle of attack higher is than the wing because of the canard downwash. You might say the downwash from the canard "stall proofs" the wing. One of the best things about a canard configuration is their stall are usually very gentle.
On a conventional configuration, the wing will stall before the h. tail for the same downwash reason.
When the forward surface stalls on both configurations, a similar aft surface effect is very necessary. When the forward surface stalls, downwash decreases and the aft surface develops positive lift. This pushs the airplane to an attitude necessary for stall recovery, less canard or less wing angle of attack.
Now let's consider how leading edge high lift devices work. Their primary effect is to allow the wing to reach a higher angle of attack before the wing stalls. On a conventional configuration, this works fine. The h.tail drives the wing to a higher angle of attack with the leading edge devices deployed than it would be capable of with no leading edge devices. The tail doesn't stall because its in the wing downwash field and its negative lift is relatively small as its moment arm to the C.G. is relatively large. The wing angle of attack gain increases overall lift and allows the airplane to operate at lower speeds.
If you put leading edge devices only on the wing of a canard, its a wasted effort. Stall is still controlled by the canard. When the canard stalls, the airplane stalls and the wing will not have developed its full lifting potential. If you put leading edge devices only on the canard, then the canard may not have stalled when the outboard wing panels, which aren't protected by the canard downwash, stall. This a very dangerous configuration. It will pitch up when the wing stalls because the canard hasn't reached its stall angle of attack and with the outboard wing stalled, there may be no roll control. To make leading edge dervices work on a canard configuration, they need to be on both wing and canard which lead to my comment in the earlier message about increased cost and maintenance. If you chose to not use leading edge devices on a canard configuration, the lift provided by the canard isn't a good trade when compared to the ability of a conventional configuration with leading edge devices to make better use of the primary lifting surface, the wing. Therefore a no leading edge device canard configuration will have more lifting surface area (and skin friction drag) than a conventinal configuration with a good high lift system assuming both have the same takeoff and landing speeds. (Note that I've left trailing edge flaps out of this discussion to keep things simple. My only comment is that if you put them on the wing, you also need to put them on the canard.)
Why not a trim tank in the canard to reduce induced drag as wing fuel burns off during cruise and the C.G. shifts forward?
For cruise, a trim tank doesn't help. The problem is that as you burn fuel from the wing the C.G. moves forward, increasing the canard loading and increasing induced drag. Having a trim tank forward only makes the problem worse, as now the C.G. is forward to begin with. Likewise, trapping some fuel at the wing tips can't delay the forward shift in C.G. as the wing fuel is burned. If you take fuel out of the wing and distribute it in the body, you lose on two counts. The body fuel reduces cargo capacity and the wing has to get heavier because it has no bending moment relief from acting as a fuel tank.
In summation, the small amount of lift which seems to be gained from having a canard makes you pay a very high price for eliminating a small tail download which often is not there in cruise anyhow. Most cruising flight for a conventional configuration has a C.G. position at or aft of the wing center of lift so the tail either has no load or even a slight upload.
Popular Mechanics is not the best place to learn about airplane design.