I'm really not sure what you hope to achieve here.
You want to build on XF - but you can't distribute that. So you're building a theme or a plugin, or both which could be shared, I guess - but if that's the case we could just go to XF.com and publish things there.
If the plan is 'let's build the next generation forum software'... stop. You can't build that on XF, because you don't own the XF codebase, and I guarantee you presenting it to Kier and Chris and co is going to go down like a lead balloon because you don't know their roadmap (nor is it how they work, anyway)
Which means the only viable plan becomes 'building from scratch or building on top of one of the open source systems' (because open source lets you do that), which means you need people who know those systems and can modify those systems. Getting from there to 'the next gen forum software' is achievable, but it's a multi-year process even when you have multiple people who already have all the skills, and already have the motivation and a roadmap in mind.
Now, I'm happy to have a conversation on that front - I have ideas on what the next generation forum software should look like, quite extensive ones. I suspect many will hate it, at first. And I can give you an idea of what the realistic estimation of time and effort would be to get there, but all destinations that aren't 'take existing systems, add existing plugins, tweak' start at 2 years.