I am thinking about the need of a guidescope which is important for astrophotography.
However, if you're going to bring several camera lens for different focal length, we might actually use them to guide each others. For example, if you're going to bring a 200mm f2.8 and a 300mm f2.8, they might be able to serve as the guidescope of the counterpart with suitable adapters.
In case the focal lengths are quite different, say 100mm and a 300mm, a tele-extender might be added to make them close. We know that the guiding accuracy might suffer if you use shorter focal length to guide longer, but that's what you have to live with when we want absolute simplicity.
Remember the good old days, my friend used a FS60C and Sky90 in that way with great success.
Conclusion is that, for relatively wide field imaging, and I know that 300mm is pushing the limit, we might not need a dedicated Guidescope.