It seems like the Invoke node will load the geometry to memory on Generation. If upstream items haven't cook the output file yet, the Invoke node won't generate any work item at all. So it seems like this node should be dynamic only. But it is not necessary to be dynamic, right?
Also, the Invoke node doesn't have a cache mode parameter and will always perform recook. Will this node getting some upgrade? It seems like it is lacking some basic function, but this node is the only Top node that runs fast and makes it easy to deal with geometry in PDG, currently.

This is addressed in 18.0 with refactors made to that node and PDG. In 17.5 the node looks at upstream output files to find input geometry. In the case of chaining multiple invoke nodes its also able to load upstream geometry data directly, however in both cases it needs to be dynamic in order to access that.

In 18.0, PDG has a new “geometry” attribute type so that work items can store in-memory geometry directly. That attribute is primarily used by the geometry import and invoke node. and the TOP SOP network. The invoke has been refactored to add support for using that new attribute type as an input and/or output, work statically and hopefully be easier to use.

Note that in 18.0 HDA Processor also includes some significant performance improvements.