The only alternative I can think of is to use your walking foot and do straight line quilting with that, following a marked line or masking tape applied to the quilt surface (and stitch next to the masking tape). Same for the ditch work. This means turning the quilt so you are always in the correct orientation and possibly having to wrestle a lot of quilt into the neck of your machine.
If you want to free motion your straight line work (aka ruler work) save yourself a lot of frustration, possible damage to your machine and yourself and buy the ruler foot.