It would be very expensive and challenging though, especially since all the stations are underground.^^ Actually it's pretty well placed to be able to serve the high 600s of Yew Tee with a pedestrian walkway across the Pang Sua canal.
Given 979's roundabout route this may be a better solution, allowing 979 to focus on the southern half of Yew Tee.
The 5-track station appears to be 1 stop north of Sungei Kadut.
And I can frankly tell you that at this point, you're highly unlikely to see both lines go to Woodlands North - that would provide too much capacity, and at what cost? Woodlands residents shouldn't be taking the DTL anyway, they should be taking the TEL to town, or bus services if they want to get to the Bukit Timah area.
Plus, if you're still concerned at that point, and if ridership justifies it (hint: right now, the answer is no), it may be time for LTA to start seriously thinking about expansion of DTL stations into buffer areas to handle longer trains (not necessarily 4 cars of 23m)