Could this be used in a pie plate instead of a springform?

Unlike the nabisco crust which was a deep dark color, this is paler, so isn’t as tempting. But King Arthur’s black cocoa might do the trick or a mix of two types?

Absolutely.

However these bakeless cookie-based crusts are often fragile. The springform pan makes unmolding and serving easier. If you intend serving the cake directly from the pie plate, go right ahead.

Yes, absolutely!