I looked into that about 6 months ago and considered adding it to SPA as an addition. Yoland - who has much more experience than I do with VA's including this one, advised me against this because he had experienced a VA that included that option. Unfortunately, instead of attracting new pilots to their VA, it had the opposite effect of having pilots abandon the VA to fly solely FSEconomy. That's why I've continued to work on our own Economy Module that can incorporate a business model into our pilot's flights while still keeping things 'in-house' so to speak. Of course my limited talents will not approach their site's Econ offering, but at SPA we offer a smorgasbord of options where almost any pilot can find something that meets their taste.
SPA Pilots are free to pick and choose where they wish to fly in addition to SPA when it comes to the various VA's that are available. However, experience (Yoland's anyway) dictates that our focus here at SPA be directed at making and keeping SPA a competitive VA that is attractive to current and prospective pilots.