This can be done very easily already. Just use the power of Photomechanic's variables and IPTC.
Just open the contact sheet, open IPTC dialog on the first photo, navigate to appropriate unused field (I suggest using Object name), write the new name. You can view the photo or view a larger version by holding CTRL-Z or ALT-Z (mac/pc). Then, just press Command-] (or CTRL-] on PC) and it will save the info and advance to next file, still while keeping the IPTC field you wrote last time selected.
So you just write the name and press Command-] or CTRL-] without having to ever use the mouse.
When you rename all the photos you want, just select them all, do Batch Rename and as the new file name, use {object} variable (or variable of whatever IPTC field you used for this, but Object is the best usually). I suggest you add {seqn} as the second variable, or use {fnm4} as the second one.
Let's say you entered names like AdamsWeddingGroup and AdamsWeddingBrideParents for several photos' Object field.
Batch rename string like this: {object}{fnm4} will produce photos named thus:
AdamsWeddingGroup4510
AdamsWeddingGroup4511
AdamsWeddingGroup4520
AdamsWeddingBrideParents4701
AdamsWeddingBrideParents4703
AdamsWeddingBrideParents4721
Where the last four-digit number is from the {fnm4} variable, which extracts the frame number from the Exif/file name (e.g. DSC_4701).
Similar with {seqn} variable which just adds automatically increased number, ie 01,02,03,...
I suggest using the {fnm4} or {seqn} in case you might have same name files, which would cause a conflict of file names and PM would append A,B,C... or 1,2,3,... to the end of file name automatically. With the fnm4 you can even easily identify the source file if you need to go back to edit it again.
Hope this helps, Frantisek