The idea I got involves a bigger but maybe better project, I may just clear the small bank, repair the retaining wall and let the semps there spread without competition from weeds and grass, theres 3 different large old tectorum colonies and 2 cobweb noid colonies that look like they would spread to fill it all given the chance. Id hate to tear that out to only plant them again, there are a few hundred!
Just a little bank clearing has allowed these to start spreading, looks like it spreads by the day.
Clearing the worst of the weeds has made the tectorum start offsetting all along the outer edge of the colonies. Theres alot more tedious weeding to get done, its a.little tough to do without stepping on semps!
I have a bigger bank that faces south, is tree shaded in summer til around 11am and then sunnny til dusk, and full sun all winter long, and its not huge, maybe 10 feet in height but about 40 feet long, and steep enoough a royal pain to mow...its just crappy fill dirt, very gravelly so the lawn that grows there is mostly weeds, but it is already very well draining so id have a great base underneath. Your block planters gave me this idea...building maybe one at a time, step and terrace the block into the bank in a section about the same size as yours, only terraced, and between sections use block for steps the same way...slowly cover the bank in 4x8 plantings with steps between to match the terracing.
Since im terracing, instead of using the block holes on the outer edges for semps, use them for sedum to "pour" out and down over, and use the inner large sections for semps. One section at a time id slowly make my mowing easier and the bank alot prettier!