Can I use a deserializer without a matching serializer?
You can avoid the need for the multiplexer and separate flip flops by using a serial to parallel shift register component. Shift registers of this type are available in logic type parts that are four or eight bits in length that can be easily cascaded to achieve the serial length (parallel width) that you need. If you do use discrete logic parts you will have to use devices that are compatible with the serial data rate. Specialized parts may be needed to achieve very high rates.

You would still need some separate logic to detect the framing of the serial data so that you can properly synchronize the serial to parallel register latch pulse.