A new BSIP has been drafted, any and all feedback is welcome.
https://github.com/blockchainprojects/bsips/blob/56_Managed_Vesting_Policies/bsip-0056.md

Any and all feedback is welcome, discussion and review can also happen in the pull request below
https://github.com/bitshares/bsips/pull/119

It will enable off-chain activities that can be settled transparently on the blockchain, and implicitly enables the creation of savings accounts for the users that are locked a certain time period to enhance fund security.

Abstract

This document outlines a feature that expands the existing vesting balances. A new vesting balance policy is introduced, namely managed vesting balances. This new policy contructed with following key elements:

• after triggering a withdrawal to the balance, the balance owner only receives its funds after waiting a certain time period (delayed)
• allows cliff vesting (if set, a withdrawal can only happen after the specified datetime)
• contains an optional manager, which is allowed to access the funds and move them to other vesting balances that have the same manager and same asset
• allows the owner of the vesting balance to deposit more funds into it after creation
• balance counts towards voting power

Summary for Voters

This BSIP introduces a new vesting balance policy, which introduces a delay on withdrawal and a manager that has limited access to the contained funds.

It can for example be used as a deposit into a CEX. Locking away funds on the BitShares Blockchain represents a deposit into the CEX, which allows the user to trade on the CEX, while the CEX does not need to be the custodian of the funds. The CEX settles the trades of the user onto the Blockchain every X amount of time and recognizes when the user wants to withdraw. With the built-in delay the CEX has enough time to settle the user balance on the blockchain according to internal trades.

Other use cases are possible too, like a promotion programm within the BitShares Blockchain (lock away asset X and gain Y% every Z time period), and of course a savings account (lock away asset X, can only be accessed after waiting X days).

The proposed approach enhances transparency and security over funds while allowing exchange businesses to offer more sophisticated and improved trading that would otherwise not be possible in a decentralized exchange. Effectively, the settlement authority has full control over the funds until the customer has initiated a withdrawal and the delay period is over. Insofar, this proposal adds limited security but significant transparency, and the benefit that the user retains his voting rights for vested BTS balances.