I figured Morris was on the right track, but his plan did not succeed given two points:
1. Axis blitz in 39 ---> no Dyle.
2. Attack on the 1st turn of fair weather between Oct-Nov 30.
Obviously we know what happens if you ignore a blitz. The second point is that since there's a good chance of only 1 fair weather turn between oct-nov (somebody wrote that on the forums, I believe), then the Allies can often do their own blitz into Belgium just before the weather turns against the Axis player, thus hindering any counterstroke. Neither condition is under the control of the allied player, however, many (most?) axis players don't blitz, and the chances are good that the allies can attack into France at the right time (i.e. the first fair weather turn between Oct-Nov '39). In my game with Tim this didn't work out - I had bad weather starting in Oct. However, versus Schnurri it was more interesting - I got perfect weather (fair on Oct 11, then Mud for a long time, then winter straight till March 1940 I think).
I'm not certain the cons outweigh the pros, but they seem to, so I'll lay it out for you as best I can.
First off, here's a shot of the Allies after they've conquered Belgium. The few extra turns to prepare also guarantees the Allies have overwhelming force. I got a bit unlucky with the "border guard" which didn't die until the third attack. Still, I had plenty left to take the Capitol.

Of course, the Canadians immediately activate...

and so the question becomes how much can the Allies drain the Axis before France succumbs?
I reckon that Schnurri and I are on a par skill-wise (we are both good, but, not ascendent, players), so I think our results were pretty much to be expected. I might as well just tell you what happened, which is that France did not fall until Oct. 40. In addition the Axis casualties were obviously much higher as you can see here.

The army unit losses were 1 German INF, 1 ARM and 1 Mech
The state of the Uk was not great -- they lost 2 Mechs and an INF and some GARS. On our last turn I built 2 INF because I was suffering the morale drop. I had no DDs in the pipeline, and 5/7 labs, but the RAF and RN were in good shape.
Here are the pros and cons:
Pros:
activate Canadians early
no morale drop
extras PP for French (and PP denied the Axis for a few turns in 1940!)
Netherlands activates at full strength
fighting under a narrow front leading to much greater Axis losses
delayed Fall of France
The Cons:
smaller convoys
extra PP for Axis when Belgium finally conquered
reduced PP for US
What effect will this Dyle plan have on the axis Fortunes? Certainly, it seems to take a 41 Sea Lion off the table, and it generally throws off their timetable, whatever their plans were: a 41 Barbarossa will be weaker, it will take longer to activate Spain, etc...The Dyle Plan seems to be a good way to execute the "bleed the axis" strategy. Sure the US is weaker, but what does it matter when Russia is waiting to go in at full strength?
Anyway, I'm just throwing this out there to see what others think.