I'd say go w/ wordpress as a subdomain of the main app, and use the Json plugin to pull in data to your existing design, you can still linkout to the blog, but

I'd say go w/ wordpress as a subdomain of the main app, and use the Json plugin to pull in data to your existing design, you can still linkout to the blog, but the main site will be easier to design using the data from the blog. ie. blog.yourappp.com and anywhere you want on the front page you could pull in recent posts or comments using the json api. That's what I use for my laravel apps.