### 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
{
    CNetAddr addr;
    CDataStream s(SER_NETWORK, PROTOCOL_VERSION);
    
    
    s.SetVersion(s.GetVersion() | ADDRV2_FORMAT);
    s << addr;
    BOOST_CHECK_EQUAL(HexStr(s), "021000000000000000000000000000000000");
    s.clear();
    BOOST_REQUIRE(LookupHost("1.2.3.4", addr, false));
    s << addr;
    BOOST_CHECK_EQUAL(HexStr(s), "010401020304");
    s.clear();
    BOOST_REQUIRE(LookupHost("1a1b:2a2b:3a3b:4a4b:5a5b:6a6b:7a7b:8a8b", addr, false));
    s << addr;
    BOOST_CHECK_EQUAL(HexStr(s), "02101a1b2a2b3a3b4a4b5a5b6a6b7a7b8a8b");
    s.clear();
    BOOST_REQUIRE(addr.SetSpecial("6hzph5hv6337r6p2.onion"));
    s << addr;
    BOOST_CHECK_EQUAL(HexStr(s), "030af1f2f3f4f5f6f7f8f9fa");