The MSP430F5504IRGZR: The 25 MHz clock rate is enough for real-time control loops, polling USB transactions, and handling sensor data at moderate rates. The USB 2.0 peripheral is a full-speed (12 Mbps) device — no host mode, but it handles HID, CDC, and bulk transfers cleanly. That saves a separate USB-to-UART or USB-to-SPI converter on the BOM. The 8 KB Flash and 6 KB RAM are tight: you will want to fit the USB stack and application code within that 8 KB, and the 6 KB RAM leaves room for a couple of USB buffers plus a modest data array. If your firmware needs more headroom, the MSP430F5xx family scales up in Flash and RAM with the same pinout — something to keep in mind during prototyping.
Package and layout notes for the 48-VQFN
The 31 I/O pins are available. The part is surface-mount only.
That removes the immediate obsolescence risk for a new BOM line.