It's been a while since you asked, but for a long time now there has existed an external program called GProxy++ that offers exactly this functionality.
GProxy++ is a tool created by Varlock, which allows reconnecting to a GHost++ server in case of a Internet disconnect, WLAN interruption, or other network related issues which would normally cause a disconnect from the game.
This works because GProxy++ proxies the connection between GHost++ and Warcraft III. If you disconnect from the game, GProxy++ detects it and starts trying reconnect to the server. Because Warcraft III automatically disconnects if no packet from the server is recieved within 65 seconds, GProxy++ sends empty messages to ensure Warcraft III stays in the game. If the reconnect is successful the game can continue. The user of GProxy++ has hereby a limited time amount. This can be set in the ghost.cfg of the GHost++ server. In some rare situations, you only have 65 seconds before you disconnect, without the change of reconnecting again.
Using it is slightly nontrivial. The original author's forums no longer exist, so you'll have to settle for this tutorial: http://wiki.entgaming.net/index.php?title=EntGaming:GProxyVarlock
This won't work on any arbitrary game. Only games hosted with GHost++ with GProxy support active will allow you to reconnect. In addition, all other players will have to wait until you either reconnect or time out - the game won't continue without you.