If you want to split your website into smaller peace, this is possible.
You will probably need to share the users between the website.
Concerning the "article", you could put them in one website to reduce the size of the DB or put a forum into another DB, ....
Concerning JReviews, there is no bridge for this extension.
If you want to share the the content of some extension, see the list of extension and the one that can be shared.
www.jms2win.com/en/list-of-extensions?vi...id=269&Itemid=53
If you share the content of some extension, the MySQL table are shared (not duplicated). So you will not save disk space.
Concerning the Search, with the "Multisites Search" plugin, it is possible to merge the results from different websites. This plugin allow searching in the articles, categories and section. Not in the content of the other extensions.
JReview is not an extension that can be share and you may have limitation concerning its configuration.
As this is an extension that is encrypted with IonCube, any problem of compatibililty must be reported to JReviews author as their code is encrypted.