The diagonals are the cross pieces in the trellis; these are very distracting to the eye and challenge as the focal point...
And while you have the idea (and the list of items) correct, all these are vertical elements, and I think you do need to do some selecting there to pick a central focal point (Can mesh two elements like the bamboo and the lantern). Maybe one other vertical element, but it needs to be subservient to the primary (much discussion in J-gardening texts about stone groupings having master and servant relations).
AND to keep it restful, more horizontal elements (think how restful a horizon line is to the eye). The other thing to think about is negative space; to my mind it is a defining feature of Japanese gardens, and we in the West have a hard time not cluttering with too much. Ponds, raked gravel, monocultural groundcovers even; all these can act as negative space.
Remember, less is more...
Scott