Have you had an opportunity to look at Julia? It seems that there is some overlap in what can be achieved - with some obvious differences: as I understand it you had a lot of c++ - that could probably (today) be linked from julia, but not "integrated", starting from a green field with Julia, ideally one could do most things in Julia - maybe with some help from rust. And Julia is not a common lisp, obviously.
But in merging a high level language and the love, it seems Julia has been successful in getting a lot of real-world, "all Julia" libraries, with "sufficient" performance.
If you were starting over today - would you still prefer to build a common lisp with close integration to c++?