Lovely quilt Lorna. I like Nancy's suggestions too. Here's an alternative suggestion as well. How about a stencil, or even a couple of different ones in the blocks. The first two are more detailed but if you had the right size they would fill the entire block with an alternative pattern which I think could be quite nice.( I don't mean these specific stencils but ones of your choosing.) The third one, though a simpler pattern is more difficult because it is not a continuous line stencil so there would be a lot of starting and stopping.
My other suggestion is that you could do a continuous curve between the points of the little squares on-point on the Irish Chain blocks.
I love the egg and dart images you posted and I have never seen that particular one on a window, fence or anything before, so thank you for that. But I am not sure that pattern would show up on the wider sashing border on your quilt because of the fabric, unless you use a very strong contrasting thread. I have used that motif several times in my quilts and love it. You don't need a stencil for it to work, just a circle template the right size. If you need help figuring it out I can tell you.