Why dont they just take a string as the argument to search() and parse it? They could use a very SQL like Syntax:

  $collection = Braintree_Transaction::search("
   orderId LIKE 'a2d%'
   AND customerWebsite LIKE '%.com'
   AND billingFirstName='John'
   AND status() IN ('AUTHORIZED','SETTLED')
   AND amount>=10
   AND amount<=20.00)
  ");