I haven't thought of that. But it's going to be more expensive than the CRT Elgamal scheme. A CRT Elgamal cyphertext would be 6 EC points. Your idea would be 3 EC points (1 from the commitment + 2 from Elgamal) plus the size of the ZK proof (probably going to be 3 EC points + 3 256-bit integers?). And it still would have the problem of requiring that users connect every 7 days to the network.
Also, the mini-blockchain only stores transactions for a limited time (in cryptonite's case it's 7 days) so if someone receives a transaction and doesn't connect to the network in 7 days, he won't see the transaction and will no longer know its own balance.