I've put some thought in to this over the past few days. I realize you said changing vehicles is not an option due to mobility concerns, but is there a possibility a different accessible vehicle might work for you? The Caravan just isn't a mod friendly platform at all and to get anywhere near your power goals in that platform while retaining reliability and driveability will be a big challenge. You also said money wasn't a consideration, so here's my best stab at a solution.
How about the Mobility SVM conversion on a Silverado/Sierra? I'm thinking maybe a 2wd with a 6/8" drop and the biggest V8 you can get in whatever trim level you choose. The 6.2 with the usual intake/headers/exhaust/tune should give you enough power and sound to put a smile on your face and the LSx/rwd platform is super mod friendly and the sky is the limit if you want to go crazy in the future with turbo kits etc.
http://www.amcmobility.com/wheelchai.../mobility-svm/
http://www.mobilitysvm.com/