propagation of &mergeable


In the below data structures, is there any way to make &mergeable apply to
the set[port]s? If I make empty_smtp_servers &mergeable, I get an error. If
I make data &mergeable, will it propagate all the way down to the
smtp_servers tables?

type SMTPServers: table[addr] of set[port];

const empty_set_of_ports: set[port] = {};

const empty_smtp_servers: SMTPServers = table()

type HostData: record {

        ## SMTP servers the host has successfully connected to.
        smtp_servers: SMTPServers &default=copy(empty_smtp_servers);


global data: table[addr] of HostData = {}

Just to be clear, what I want is the below two lines--run simultaneously
on two nodes--to result in data[]$smtp_servers[]
containing both 25/tcp and 587/tcp.

add data[]$smtp_servers[][25/tcp];
add data[]$smtp_servers[][587/tcp];