Knees are greatly assisted by 2 walking poles.
I agree that down seems a lot worse on the knees to me than up.
But if steep climbs are an issue, then there is a steep section up Hansons Peak. This can be avoided by going behind the peak and ascending up to Twisted Lakes.
However - that does add more down then up and the track is a lot rougher underfoot.
If you are using Hansons as an alternative to Marions Lookout, but then heading back to the OT along the Face Track - that is also a very rough route underfoot with a steep climb just before Little Horn.
Personally - I love the Lake Rodway area.
But you would need to weigh up the pluses and minuses
- via Lake Rodway - shorter day 1 walk, less climb, but rougher track. Very Steep [with chains] on final climb to Hanson - rest is pretty good. Means the Second day has a steep climb out and extra kms added to the walk from Waterfall Valley to Windamere. [Also rules out climbing Cradle on Day 1 - but could add Barn Bluff on day 2]
- via Hanson and Face Track - longer walk and much rougher track. Short steep part up Hanson [steeper but less height than the climb up Marions] and short climb section on Face track.

- Ascending the short chain section to Hansons Peak
- Normal route up Marions - steep sustained climb up but good track thereafter. Longer day 1 distance to Waterfall Valley than to Lake Rodway. Can climb Cradle [or Barn bluff] as a side
- there is a fouth option that we took last year - from Lake Dove to the Face Track via Lake Wilks. That involves a steep climb past the Ballroom Forest and then a bench before another steep climb assisted by chains. But it is an alternative to Marions of similar length, the views are fantastic and still allows for Cradle to be climbed. A lesser climb and still worth while is the short pad up into the Cradle Saddle from the junction with the Face track for a view of the back of Cradle.

- The chain section above Lake Wilks

- View of Rodway valley from the Cradle saddle