### 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
{
    complete = false;
    const auto time = GetTime<std::chrono::microseconds>();
    LOCK(cs_vRecv);
    nLastRecv = std::chrono::duration_cast<std::chrono::seconds>(time).count();
    nRecvBytes += msg_bytes.size();
    while (msg_bytes.size() > 0) {
        
        int handled = m_deserializer->Read(msg_bytes);
        if (handled < 0) {
            
            return false;
        }
        if (m_deserializer->Complete()) {
            
            uint32_t out_err_raw_size{0};
            std::optional<CNetMessage> result{m_deserializer->GetMessage(time, out_err_raw_size)};
            if (!result) {
                
                
                mapRecvBytesPerMsgCmd.find(NET_MESSAGE_COMMAND_OTHER)->second += out_err_raw_size;
                continue;
            }
            
            
            mapMsgCmdSize::iterator i = mapRecvBytesPerMsgCmd.find(result->m_command);
            if (i == mapRecvBytesPerMsgCmd.end())
                i = mapRecvBytesPerMsgCmd.find(NET_MESSAGE_COMMAND_OTHER);
            assert(i != mapRecvBytesPerMsgCmd.end());
            i->second += result->m_raw_message_size;