Auto-X may be different -- I just don't know. With one car on the course at a time the risk of accident is greatly reduced, and the speeds are lower of course.
For road racing and vintage events I believe there are condition-based provisions for mounting a fuel cell in the cockpit area, but only if the fuel cell is contained within a metal enclosure, which is itself further separated away from the driver with another metal bulkhead that totally separates the cockpit from the container carrying the fuel cell. The floor under the fuel cell must be designed in such a way as to ensure spilled fuel does not accumulate (for obvious reasons), and any fuel lines running through the cockpit must be covered and designed to deflect fuel spray should one of them burst.
This assumes a proper FIA FT-3 spec fuel cell, such as those from Fuel Safe/ATL. In European FIA Appendix K historic events they still allow you to run with foam-filled aluminum tanks last time I checked, but here in the USA a proper fuel cell is required by almost all race sanctioning bodies. And if you're using a fuel cell then you would want a fire suppression system to cover the cockpit and engine bay.
All in all, cockpit-mounted fuel cells are a lousy idea. Keep the fuel as far away from the driver as possible. The risk to driver safety greatly exceeds the improvement in performance. My 2 cents...
Best Regards,
Andy