would it make sense to payout witness pay partly in liquid steem? (for example 50% liquid steeem and 50% SP)

If witnesses won't have to power down it would look much better to new investors.
Although having the 2 founders powering down sends a total wrong sign to investors. My friend who runs a VC firm was considering putting 500K into Steem. While researching they saw you and Ned powering down.
As founders you should not power down or at least if there is a reason for power down than the reasons have to be openly explained to everybody (Diversifying is not a reason an investor will accept from you guys as founders)

If you are employed by Steemit Inc. your salaries should be set high enough that you don't need to power down. I talked to many people on Steemit and everybody says, well the founders are powering down so am I.

Maybe my idea doesn't make sense at all, but this way

Witnesses won't have to power-down
Witnesses who were not powering down will power-up the Liquid Steem (looks good to investors)
Investors and users are encouraged to invest long-term into Steem Power

And for god's sake everybody working for Steemit Inc should stop powering down. I never heard of a startup where you can start cashing out your shares after 3 Month of initial launch.

If you are not able to pay yourself a 6figure salary which will cover all your costs go fundraising with Steemit Inc but please stop selling your STEEM and discouraging Investors from putting money into your baby.

I truly believe in your idea of token based economies and Steem will disrupt social media or other fields for ever if done right.