I've had to do it custom every time. I'd highly recommend looking at using the domain seperation feature if possible. I'd also tread lightly on trying to extending data segregation into software asset management, for example software installs don't have a company field on them, nor do other tables like software usage and reclaimation candidates. Also think about how how software entitlements may need to get multiple entries (e.g. global buys the licenses, but the licenses are managed at a 'local' level)
Also evaulate the impacts to processes such as change management, where the change might span CIs/Assets that don't fall cleanly into a one data segregation unit. Or how Transfer Orders will work if there is a need to request a transfer of assets across data segration boundaries.
Also be ready to work through performance issues and useability issues.
