Wow... Lets break down a few issues here:
1- Accuracy is based on distance and angle of attack, Period. You can't have both!
This takes me back to the old VCA days. The camera can only see what your eyes can see. VCA, Machine Vision, or AI, whatever the latest trite trend name is in the industry the technology is based on pixel analysis. Yes, we have more pixels than we did in the 80's and we have more processing power to analyze those pixels, but the baseline is the same, you can't read it? the LPR won't read it either.
When you introduce steep angle of attack the license plates are no longer rectangles, the fonts change and the spacing between them decrease. Which is why most LPR manuals insist on 30 degrees.
2- Distance reading is pure optics. LPR can read from a mile away if you have the proper lens, BUT again you are sacrificing accuracy as you add shake, pollutant particles and bad weather such as fog, rain and snow to the equation.
3- Cloud based LPR is a bad idea all around! If you use LPR for access control you will piss off the residents as they wait by the gate. If its used in high-speed application by the time you get the result the vehicle is gone. SPEED is a major factor in the usefulness of any LPR system.
4- Compatibility and Integration with ONVIF is meaningless. Stop thinking about it as a security camera in which you want to stream video! it is not... LPR main purpose is to capture a few quality snapshot which will provide an accurate read. You want to stream video from the road scene? use a separate HD camera with a wider view. the LPR camera performs best when it focuses on one lane.
Which gets us to the multi-lane requests
5- Multi-lane reduces accuracy of the reads, AND of the identification of the vehicle. Multi lane LPR relies on VCA to first capture the vehicle, capture the plate area and then run the OCR engine. The process decreases accuracy the more lanes you want to cover. It is completely useless for access control.
Finally, the best way to identify a vehicle in the scene is what we do in access control applications. We tie the LPR to a vehicle induction loops. We use the camera Alarm Input to trigger the LPR/OCR engine. Vehicle Induction Loops are used in traffic lights all over the world and are the most reliable tool for vehicle presence.