One one hand, that sounds extremely convenient. On the other, I shudder thinking what a malicious app could do with that 😆
Edit: Unless you're talking about doing it through TWRP. I had to flash that over fastboot, but once installed to the recovery partition, I could boot into that and install the rest of Lineage and extra packages straight from the SD card. Updating the system was just downloading the new Lineage .zip to the SD card, booting into TWRP, and clicking install.