We are trying to achieve something like:

 1) Use selenium to navigate web application and Jmeter to capture network traffic.
 2) Would like to combine requests based on business case using Transaction controller. for e.g. - Requests could be combined in transactions Login, Add items to cart, Checkout, Payment.
 3) Transactions created in Step 2 helps in combining response times of multiple requests.
 4) Don't want to add transaction controller manually.
 5) APIs can be exposed using which transaction controller can be added and start/pause/stop recording from java code and not from UI. Users can override it via plugin.