I would not worry about a 90 minute connection time. Your bags will be checked through and as mentioned AA owns the problem if something goes wrong. With the timing of the BVI leg your departure out of PHL is early and probably a first flight of the day. Those tend to have very high on time performance.
We have had a very difficult time getting the local airlines to honor baggage issues. Most times they have insisted the guests return to the airport for their own bags and will not deliver them to CGB as they would in the US. Because they also refuse to tell you if the bag made it to EIS, it often takes many international phone calls and a couple of taxi trips.
Try to carry-on!
They only advantage is you normally don't have to deal with the grumpy officer at customs because the late bags usually just pass thru.
