Maybe I misunderstood what you’re saying about running a hose directly into the trash can but you need the bag (or some other kind of filter) to let the air flow through. A hose from the impeller directly to the closed can would blow the lid off and send debris everywhere. Or, if you did a great job of keeping the lid on, the system wouldn’t collect any debris from the planer.
If you made a big fitting that the zippered end of the bag could fit over, and that fit tight on the trash can, and that the hose from the impeller fit into, then you wouldn’t have to mess with the bag as much (just bang on the sides occasionally), but you’d be better off to buy an inexpensive dust collector, and maybe modify it a little, take it apart and mount it up out of the way on the wall.
If you think through the evolution of small shop dust collectors you can choose features that would suit your shop better. The first version that went beyond what you have was to add an upper bag so flow would not be impeded even when the lower bag became full. Next, the lower bag was replaced with a can. Then the upper bag was replaced with a pleated filter (and often included an integral shaker to clear the pleats). Cyclonic separation was added too.
The easiest improvement for you setup is to get a bigger bag. Next would be to hang the bag upside down over a trash can with a big Tee fitting in between the bag and can. That would probably be satisfactory.
