Chugalug you wrote:
Drips of fuel from wings, damage to tyres, cracks in windscreens, u/s systems etc, all offered as "fit to fly"
I know what you're saying, but the examples you quoted are always referred to documented limits, so there is never any decision based on front line opinion, only. Cuts in tyres, cracked windscreens, small fuel leaks, once entered the maintenance document, are always checked against limits in the books, taking the no-go option if there is any doubt. If the defect is clearly in limits and hasn't worsened (and they are usally checked before every flight or daily), the crew are obliged to accept the engineering decision. If the fault isn't in the books the front line engineers are obliged to seek guidance from supporting organisations; usually the IPT, who might then take advice from the manufacturer, etc.
I think we are all singing from the same songsheet, here.