High volume "on-chain" Bitcoin transactions above the block limit

[bg002h]

Lets suppose I'm a big receiver of Bitcoin (like Bitpay). Lets say I'm really a big business with 100 transactions per second. Could I receive private keys instead of having my customers try to squeeze their transactions into the block chain and then construct one transaction with many private keys and "change return" public addresses from my customers to transfer the coins to my address and dispense change to each customer?

Is there any advantage to this approach in terms of block size limit (presumably a limit on data size, not #of transactions, but I'm uncertain) or fees? Or is this just a hard/risky/generally pointless approach?

[DeathAndTaxes]

No not really.  The combined tx may be slightly more efficient in terms of space if the private keys were of exact size however if you need to include a change address for each tx the combined tx is going to be just as large as the sum of the individual transactions.   It might be slightly smaller but not significant enough to warrant the increased complexity.  Also the private keys are vulnerable to double spend until the combined tx is created and confirmed in a block.