You COULD get an older desktop or server, install Linux and VNC, connect it to your wifi, and stash it under the stairs / wherever. Then your lappie can VNC into it and use its (undoubtedly much better) RAM and CPU to run heavy apps. I did this recently during a summer heatwave here.
We have a NAS.
A commercial NAS is great for storage, but probably no better than your laptop for RAM and CPU, sadly...