Ask HN: How to allocate startup equity between parttime and fulltime cofounders?

I'm working with my cofounder on a software startup. While I'm working on the startup fulltime, my cofounder is involved part-time (i.e. works a separate fulltime job). I work on the technical and business side of the startup whereas my cofounder works on the UI/UX design aspects. The startup is not revenue generating at the moment, but likely will be by Q3 2018. The cofounder will jump in fulltime once there's some level (TBD) of funding or revenue.

I want to set up a LLC and for that my cofounder and I need an operating agreement, which details how we split equity, set up vesting, etc.

The standard advice I get is "a founder is someone who works fulltime", "founders need to split equity equally," etc. (see references below). But, I don't see how that advice would work for me. I like working with my cofounder and although not contributing to full potential my cofounder is a talented designer. My cofounder acknowledges that I put in the lion's share of the work and is willing to take less than 50%.

I think that in addition to the unequal split, my cofounder's equity needs to vest at a slower rate than it does for me and there has to be a clause where after any significant event (funding, revenue, etc.) if the cofounder doesn't join fulltime the cofounders equity will have to be forfeited.

Could you chime in on the following questions:

1. Do you foresee any problems (legal, potential founder breakup, etc.) with the unequal equity and slower vesting for my cofounder?

2. How would you split equity, set up vesting and what kind of commitments would you need from a part-time cofounder in this scenario?

Please do point out if I'm missing anything.

References:

1. https://avc.com/2011/04/how-to-allocate-founder-and-employee-equity/

2. https://gist.github.com/isaacsanders/1653078