ST doesn't sell ST-LINK/V2 STM32F103 parts, although binaries can be found to facilitate this.
The main difference between the on-board and external stand-alone devices is the use of logic level translation for the JTAG/SWD pins based on the VTarget provided by Pin 1 of the ARM 20-pin JTAG header.
I'm sure one could find a schematic for the boot-leg devices if you looked for them.
ST does offer the ST-LINK/V3 in a module form for placement on user boards. Perhaps review that.
