Hi. Adding manual payment just on hosted page for handling customer data and setting invoice to be paid offline is a feature I'm waiting for. Many B2B especially those BIG process 95% transactions offline - with checks, wire-transfers etc.
Since authorize.net supports it and even ACH - it could be awesome feature for Chargebee
We're working on providing a lot more flexibility within the hosted pages and a checkout option for offline subscriptions is certainly in our features list. Do stay tuned. :)