Hi Ken
For the other boards e.g. F3 and F4 (well also the F103 as well really), you could look at what Avik has done
As he has tried to write the same thing from the ground up using the CMSIS headers and cpp files, for which there are versions for all the variants (though there may be some issue with copyright and licensing if you look at the fine print)
But at the moment, the only board I know for sure works with Aviks repo is the F373 as he has built his own boards based on the 373.
The downside is although Avik's repo has the possibility of being capable of supporting loads of different boards, from what I understand its not a full featured in terms of Arduino support as the repo I inherited from Bob Cousins, which he converted from libmaple
And for a lot of people who want to use the Maple bootloader, Avik's repo would take even more work to make compatible
BTW.
Have you looked at the necessary hardware changes to make your boards work with the Maple bootloader, as they could then not need a USB to Serial adaptor or STLink etc to upload.
The Maple bootloader is not perfect, but it is fairly useful.
AFIK, you just need 1 P type FET (or PNP) transistor and 2 or 3 resistors in a small circuit connected to one of the USB data lins (I cant remember is its D+ or D-), and also one pin on the uP into the gate / base of the transistor to trigger a USB bus re-enumeration by the host machine.
Let me know if you need more details, and I can send you links to schemetics (my personal favourite if the iTead Maple, which is FET based, but I have seen others using a bipolar PNP)
Anyway, at the moment, I think all of our aims, is to get libmaple stable and porting libraries so that they will work on STM32 to the best of its ability
Cheers
Roger