Ask HN: Replacing a tech co-founder

About us: Setup a business 18 months ago, and incorporated 8 months ago. I'm the back end tech lead (and business, marketing, etc), and my co-founder is front-end. I'm appalling at front-end/design. Co-founder is going to exit soon - he can’t commit much beyond september, so we’ve agreed he’s going to hand back probably 50% of his stake, keep the rest for recognition of the work done to date, and we’ll go our separate ways - this is all fine and amicable. (Not sure if relevant - front end has just been rebuilt in react.js) There are two other people knocking round with small equity stakes (currently 10% each, about to be reduced for a variety of mutually agreed reasons), and me and the other main co-founder each have 40%.

About our position: We have early non-revenue traction, and a reasonable understanding of who uses our system and how - we're building pay functionality now, and will land it in a few weeks time - the idea was to run that out till Christmas, and then evaluate whether or not to continue. (With hindsight, I would have done this last year, but you live and learn.)

Question: what should I do to replace him? I have two needs right now - one is for customer relationship marketing while I build back end, and the other is design/front end stuff - but that should diminish once this build is landed in September.

If I need to find another ‘front-end guy’ for this - would you go and look for another ‘co-founder’ type to replace him (bearing in mind I’ll have 70% ish of the company to play with in terms of equity), or would you go for ‘employee number 1’ type approach? This will be a sort of 5-9 gig, and unsalaried until we hit funding post Christmas (which now that my partner's leaving is definitely the plan - he wanted to bootstrap the whole way).

I think what I need is the marketing guy (significant options/ equity) to replace me, I'll do front-end maintance, and post-funding hire a salaried front-end dev -thoughts?