A point in the right direction

GPS and WiFi at the same time should be no problem on the Pico (or original Espruino) - Most GPS connects via serial, while WiFi uses either SPI or Serial. Since the Pico has 2 serials, you're good to go on that front.

While the same is possible on an Arduino-type board with two serials (like mega, m1284p or t1634), I find working with network-aware stuff on Arduino to be very unpleasant, as you're working at two very different levels of abstraction. For example, consider working with strings on Arduino - do you use Strings and fragment your ram or c strings and deal with fixed size buffers and remember to check array bounds obsessively? On Espruino, strings work pretty much like a sane person would expect them to, and how they do in most civilized languages