It seems the latest dev preview build 8.10.14203.206 not only brought scheduling of updates, but now if your phone has MicroSD card support, it can use this memory for phone updates.
Install updates when you want by scheduling them for a time that works best for you. And if your phone supports SD cards, it will now detect if you’re running low on space when updating and use the SD card. (Scheduling an update is available after updating to build 8.10.14203.206. Support for using your SD card for updating your phone depends on your phone model and manufacturer.)
If you remember, the OEM documentations mention that use of MicroSD card for phone updates is a new feature of GDR1, so while the feature was present and may have been disabled earlier, seems this build has enabled it for everyone, if the manufacturer allows it.
You can read the full Windows Phone 8.1 GDR1 or update 1 changelog at our dedicated page.