No, while it is nice to donate earning to help out Musing.io to lease Steem Power (SP), it may not be very sustainable, both for the person donating and Musing.io.
A better way to help Musing.io would be for interested users to delegate our own SP, in exchange for a proportional share of the curation rewards. This way, Musing.io can increase their effective SP and increase it's upvote value, and those delegating will still benefit from the SP they delegated. It will also be sustainable for both parties, since on Musing.io's part, any share they give to delegators will be, in essence, earned by the delegation so there is no additional cost. For the delegators, on the other hand, since they are not simply giving away Steem, and will actually earn some rewards, then they are more likely to continue the delegation since there are also no real losses, as well. The benefit will be long-term.
Furthermore, all the benefits will also be shared within the community, and not used as payment for a delegation service.
No, while I would gladly contribute in the form of a % of beneficiary rewards, I don’t think leasing SP is a smart decision. Leases need to be constantly renewed and the market price can change at any time, I would rather see beneficiary be used to power up. Powered up SP is also much more sustainable, even if it grows less fast. It is “yours”, where leased SP is poor math and long term a loss operation.
That said, currently beneficiary rewards are all paid out in the form of vests. Starting HF20 beneficiary rewards will be paid in the same structure as the settings for the original post (which will for most be 50/50). But rather than the liquid beneficiary rewards then being used to lease SP, I think it is important that they are used for development and maybe even as wage for the team as well.
Even a founder needs to make a living and the possibility of a stable revenue stream is an important psychological milestone and achievement in the evolution of a startup. Also, a factor of stability which allows the founder/team to continue focusing on their venture.
PS: in the current setup of Musing it isn’t really possible to set beneficiary IIRC.