Fw4: Managing lists of IP blocks? Verify reverse route?

With the move to nftables for fw4, I'm returning to trying to use UCI / LuCI for firewall management.

A couple things that I'm used to doing with either hand-crafted nftables rules or other systems I didn't immediately see a good way to manage.

If there are some helpful suggestions for these, I'd appreciate it.

Defined lists of IP ranges

For example, IPv4 "bogon" lists are around a dozen IP ranges. In a file-based approach, I'd define and use a set, such as

set blackhole_ipv4 {
    type ipv4_addr
    flags interval
    elements = {,              # "default",             # RFC 1918,          # bogon-bn-agg.txt 2017-08-17,            # loopback,         # Self-configured DHCP,          # RFC 1918,           # Vendor co-opted print servers,           # NET TEST,         # RFC 1918
        #,          # RFC 2455 (NOT IANA; for Harvard,for BMWG)
        # should be           # RFC 2544: Benchmarking,        # NeXT-Default:,         # RFC 3068,        # bogon-bn-agg.txt 2017-08-17,         # bogon-bn-agg.txt 2017-08-17,            # bogon-bn-agg.txt 2017-08-17
ip daddr @blackhole_ipv4 \

Is there UCI support for this, short of repeating the list everywhere it is used?

Verify reverse route

A common feature of other OSes is the ability to check an incoming packet's IP address against the routing tables and determine if source address on the packet either or both arrived on the interface that a return packet would exit on, or that the source address is at least reachable through that interface.