Default fixed "gwei - gaslimit" as advanced setting

There are some cases which you don’t care to overpay ethereum fees.

For time sensitive gas wars it would be very convenent to bypass the automatic gas calculations from metamask and just go with fix settings.

For example I would like to be able to simply fix " price: 500 gwei - gas limit: 52000 " until I deselect the option.
Of course a big warning sign should be implemented in the user interface if this mode is on.