Having a subdomain running ML Wordpress Theme can run in parallel with the main site, as long as we follow similar design language with the main site. I personally feel that setting up this is slightly easier than custom build theme. For short-mid term, I would suggest using ML Theme thats out there; though ideally the best is to create our own theme. With the latter will take time.
Yes, apologies, WP means wordpress. too many abbrev… 
as for moving forward, here is my preliminary thoughts/steps of the solution (though will need further refinement) as I do have basic knowledge of building websites via wordpress and limited knowledge in php and html;
- creation of subdomain & installation of Wordpress
- installation of WP ML theme & relevant plugins (ML, analytics, geofencing, etc)
- users/translator/editor creations
- consolidation existing articles to blog.indexcoop
- porting over / matching existing translation with existing articles
- optimising for SEO/SEM
- publish/ making the blog live