### FEATURE REQUEST

Currently, when a bitcoin node is set up with a connection to both TOR and normal IPv4/6 internet, the 8 outbound-only connection slots, almost always get filled with nodes connecting over IP.
Adding a config option, which would try to ballance these connections based on what kind of network they go through, would be benefficial in many ways:

1. It would add edges between bitcoin network on TOR and normal internet, reducing delays, and the risks associated with an attacker isolating a part of TOR-bitcoin-network from the rest of the world
(Or an ISP/government man-in-the-middling all the normal IP connections)

2. It would help hide/annonymise normal user's transactions from his/her ISP, by mixing them with TOR-outbound ones

3. It would reduce the stress on normal general purpose TOR exit nodes, as users would more likely/reliably connect to TOR-IPv4/6 bitcoin nodes instead of exiting into normal internet first, and then connecting to default IPv4/6-only bitcoin nodes

I understand it is possible to create such bridges already, by forcing connections to TOR-only nodes, or by just running a node with lots of inbound slots, but I think the proposed option, would greatly increase the number of such relays, and remove the need for user to maintain a TOR-node whitelist, by handing this work off to normal bitcoind connection finding algorithm.

This could be implemented as a minimum number of connections for each network, or just a simple evening boolean switch. (Which could be enabled by default for bitcoind installs with TOR connectivity)

In the future, if bitcoin was to support a new network type (for example cjdns/I2P/GNUnet), this option would help establish a presence on the new network faster

bitcoind: 0.15
{
    FastRandomContext random_context{true};
    for (int i = 0; i < NODE_EVICTION_TEST_ROUNDS; ++i) {
        for (int number_of_nodes = 0; number_of_nodes < NODE_EVICTION_TEST_UP_TO_N_NODES; ++number_of_nodes) {
            
            
            BOOST_CHECK(!IsEvicted(
                number_of_nodes, [number_of_nodes](NodeEvictionCandidate& candidate) {
                    candidate.nKeyedNetGroup = number_of_nodes - candidate.id;
                },
                {0, 1, 2, 3}, random_context));
            
            
            BOOST_CHECK(!IsEvicted(
                number_of_nodes, [](NodeEvictionCandidate& candidate) {
                    candidate.m_min_ping_time = std::chrono::microseconds{candidate.id};
                },
                {0, 1, 2, 3, 4, 5, 6, 7}, random_context));
            
            
            BOOST_CHECK(!IsEvicted(
                number_of_nodes, [number_of_nodes](NodeEvictionCandidate& candidate) {
                    candidate.nLastTXTime = number_of_nodes - candidate.id;
                },