Time to build a display model using those tyres, and get some new ones. ?
Tyres with fine cracks like that will not pass a roadworthy, so are not legal.
I've had a vehicle roadworthy rejected for that reason ( I knew that, but wasn't going to fit new tyres unless the rest of it passed)(later tyres, not even beaded edge type).
Having a tyre blow and come off a rim is not pleasant with a beaded edge, since the tyre can escape and jam up the front wheel = a good reason why well-base safety rims became popular ?
Someone was commenting that tyres with long lasting nylon sidewalls may be the go, or are what is needed to be manufactured, since the tyres 'wear out' just sitting around. Not entirely sure if this is possible...
Opethiselps.