What about a home server/network drive? This is essentially the same as windowpain's suggestion, but likely a little more stable. Hardwired of course, to ensure connectivity, and you'd still have to force yourself to save everything to the network drive, not on the local drives.
Sound like a hassle? For home use, it would be. And the fact that your MacBook would need to be hardwired almost all the time, reducing it's portability to near-zero.