Feature request: alternate json profiling mode?

Yet another possible improvement for people looking for performance issue causes.

With current json profiling flag, taking any meaningful performance measurements is very hard, as files created are massive, hard to open and even harder to share with the community. This especially impacts situations where the issue looked for actually happens after some time of gameplay. So here's a suggestion to change that:

Variant 1: create a -json_fast_profiling flag. When enabled, it would, for example, replace the functionality of the PrintScreen key: when pressed, it would start a short period of data logging into a new, separate json file. The period could be predetermined (for example, 10 seconds) or set by an argument for the flag (imagine -json_fast_profile [capture time in seconds]).

Variant 2: similar to the first one, but the logging would be started with one key and stopped with another key, eventually just toggled by a single key (would IMO require a visual information, something like "currently logging into JSON file"). Maybe this mode could be enabled by setting the capture time argument for the flag to zero?

Such a solution would, most importantly, let players start logging data multiple minutes or even hours into the gameplay, allowing them to easily catch the sought for problem in the JSON log. It also would allow to minimise the size of output files while still holding important information in them, which would help greatly in browsing and sharing them.

Discuss?