It's possible, but "possible" and "optimum" are two different things.
From this structure, you could set up a list view layout based on OrderLines that includes a portal to AsseemblyLine to list all components for a given OrderLines record. Since the number of related records will likely vary for each OrderLine record, you'd use a portal that is many rows taller than you'd ever expect to need and set it to "slide up" and "resize enclosing part".
It would also be possible to set up an additional group of table occurrences with different links such that a script could set some global match fields, pull up the needed set of assembly line records on a layout based on the same. The global match fields would "back link" to the correct records for Site, Orders and OrderLine to include that data on the report. This would make possible a List view type report with Sub Summary parts grouping the different Assembly Line records by the correct OrderLine data. The resulting report can be much more flexible than the portal method I first described.
Thanks for that, I'll try your suggestion of using global match fields.