Using the encoder sounds very logical; turn for value and push for gate on/off, I like it. The 8 soft keys could be used for selecting the windowing of the sequence perhaps?
First push of a soft key selects the start, the 8 buttons divide the sequence (whether the length be 8, 16, 32, etc) by 8, so soft key 1 is the beginning, soft 2 is 12.5% of the total length, 3 is 25%, etc. The second soft key push selects the window end location, in the same manner. If soft key push 2 is sequentially earlier than soft key push one (so the end is earlier the the beginning) the sequencer reverses direction. Changes to windowing should probably be synced till sequence end.