Do you know that the IP connection has been established at time (4)? With DHCP / WiFi / WPA / ARP / Zeroconf there is data-link renegotiation that could easily take 5 seconds between carrier on and ability to pass even one IP packet.
If this is so, The SSH session may not be the limitation, and forcing a TCP resend wouldn't help at all.
Dunno, I can't reproduce it. I had an open SSH connection between machine .2 and .3 with .3 printing the time to stdout every second. The two machines are running vanilla Ubuntu Lucid and connected through a boring WAP/Switch/Router. The machines are DHCP configured. I pulled the cable from machine .3 and waited a scientifically accurate (looked at clock) interval of 60 seconds. Here is the packet trace:
No. Time Source Destination Protocol Info
18 8.479990 192.168.2.3 192.168.2.2 SSH Encrypted response packet len=48
19 8.480024 192.168.2.2 192.168.2.3 TCP 56670 > ssh [ACK] Seq=1 Ack=433 Win=1002 Len=0 TSV=2804876 TSER=44100246
20 87.619215 AsustekC_f1:59:70 Broadcast ARP Who has 192.168.2.2? Tell 192.168.2.3
21 87.619221 AsustekC_24:9c:85 AsustekC_f1:59:70 ARP 192.168.2.2 is at 00:1a:92:24:9c:85
22 87.619527 192.168.2.3 192.168.2.2 SSH Encrypted response packet len=48
23 87.619545 192.168.2.2 192.168.2.3 TCP 56670 > ssh [ACK] Seq=1 Ack=481 Win=1002 Len=0 TSV=2824661 TSER=44120031
It took about 200 microseconds for the session to resume. I used the standard Wireshark for the packet sniffing.