Best way to connect your site (buddypress-like)

Hey.
I have messed around with a theme, now that I’m finished after a few days, I face a problem.
I’m building a blog/community site, and I’d want to connect the whole site (blog, forums, profiles) all into one.
Like buddypress does.
So that people won’t have to register to my forum, for the blog, you get my point.

So my theme doesn’t support buddypress out of the box, what can I do?
I’d prefer to use my existing phpbb forum instead of bbpress as I don’t like it at all.

Do you have any ideas how I could do this?
A generalized menu/control panel structure like buddypress has in the top of your page would be ideal, but I’m ready to sacrifice it for not using bbpress.

Any ideas, oh and the theme I’ve been working on is Arras, I made a child theme to it.