I'd like to be able to specify a function for default values within a schema

The following schema use currently causes an error, due to the default timestamp field expecting a number, not a function:

export const TestSchema = {
    name: "TestItem",
    properties: {
        videoId:        "string",
        published:       "int",
        timestamp:      {
            type: "int",
            default: () => Math.round((new Date()).getTime() / 1000) 
        }
    }
}

The default function returns what is expected (a number). Could support be added to calculate default value functions? Or would that add to much overhead? I think it'd be perfect for use cases like this where you wish to store the current timestamp