The lower side of the saucer section of the canon Constellation
made use of the upper half of the refit connie rather than the bottom half, so I might make that structure more symmetrical on your version as well. In other words, the "B-C" command gondola from the top could be repeated on the lower half of the saucer as well.
Also, the impulse units utilization of the "impulse crystal" is very much a TMP refit thing, so I would suggest some other feature here, such as the "linear accelerator" on top of the TOS impulse deck. Of something more along those lines anyhow.
Besides those little technical hiccups, I think the illustration is well done.