Code injection for an ISP

Internet Content Injection/adaptation for an ISP: I work an large ISP. We need to Inject HTML/Java Script code in all web Pages that are served to subscribers in HTTP. Right now we are not planning to do this for HTTPS traffic. When our ISP subscribers browse any HTTP website, the HTML/Javascript should get injected. This should happen in all the HTML type response. Below is the sample script that needs to be injected in every http response. The above line needs to be injected just before the tag. Attached herewith the schematic diagram for the placement of the solution. Following are additional points: 1) Solution will be placed in each ISP location, as in-line solution. Optionally if we are able to place the solution in Mirror/Tap/SPAN traffic, it will be added advantage. 2) HTTP traffic percentage would be around 10% of the overall traffic. While proposing your solution it might be a good idea to make the 90% of non-HTTP traffic to simply pass through without any processing. 3) 150Gbps is the current over all throughput for 1 location. This is growing rapidly. 4) Latency created by the solution should be very low so that it is not noticeable now and also in the future. 5) If this solution fails or causes any performance issues there must be a way to by-pass the solution so that our subscriber's would not get affected.