Many people who do this just swap hard drives between their online and offline 360 but there are those who want to use an arrangement like yours.
360 gamertags are tied to live (that is to say you can get the info back if you lose it- see recovering gamertag) but I am not sure exactly how this will work for you.
Most people who go this route have one solely for offline (usually an old banned one) and one that is online.
This USB stuff from the last update did change a few things in as much as you can dodge the "move only" nature of the memory card more easily (copying profiles could not be done with a memory card and nothing else which could get annoying) by simply cloning the USB drive/files on it in between shifting 360s.
I have not really kept up with USB hacking (they use a nominally different format to the regular 360 formats/those your 360 uses internally) but there are tools http://www.xboxhacker.org/index.php?topic=14850.0 and the underlying logic is the same.
Equally I have a JTAG box so I am afforded a few more luxuries than a stock setup (although you could just get/make a drive reader or open it up and plug it into the sata and do the same thing) in that I can put any files anywhere I like.
Otherwise you are just facing a minor variation on the age old problem of having two machines and wanting to do some work on both of them except without the ability to say ahhh screw it and easily use a fileshare of some form.
The more elaborate form would come in that of profile editing to create "best of both worlds" profiles out of the two machines but that is a decidedly more risky option if you care about Live (they really really do not like profile editing).
Suffice it to say you can easily trade profiles between consoles, achievements seem a bit of a boring use for the effort (save games on the other hand.....) but the theory holds.
Finally if you find yourself editing a drive then http://360.kingla.com/ and http://www.se7ensins.com/forums/topic/4008...ning-explained/ are worth a read/knowing about.
360 gamertags are tied to live (that is to say you can get the info back if you lose it- see recovering gamertag) but I am not sure exactly how this will work for you.
Most people who go this route have one solely for offline (usually an old banned one) and one that is online.
This USB stuff from the last update did change a few things in as much as you can dodge the "move only" nature of the memory card more easily (copying profiles could not be done with a memory card and nothing else which could get annoying) by simply cloning the USB drive/files on it in between shifting 360s.
I have not really kept up with USB hacking (they use a nominally different format to the regular 360 formats/those your 360 uses internally) but there are tools http://www.xboxhacker.org/index.php?topic=14850.0 and the underlying logic is the same.
Equally I have a JTAG box so I am afforded a few more luxuries than a stock setup (although you could just get/make a drive reader or open it up and plug it into the sata and do the same thing) in that I can put any files anywhere I like.
Otherwise you are just facing a minor variation on the age old problem of having two machines and wanting to do some work on both of them except without the ability to say ahhh screw it and easily use a fileshare of some form.
The more elaborate form would come in that of profile editing to create "best of both worlds" profiles out of the two machines but that is a decidedly more risky option if you care about Live (they really really do not like profile editing).
Suffice it to say you can easily trade profiles between consoles, achievements seem a bit of a boring use for the effort (save games on the other hand.....) but the theory holds.
Finally if you find yourself editing a drive then http://360.kingla.com/ and http://www.se7ensins.com/forums/topic/4008...ning-explained/ are worth a read/knowing about.