its not a problem of hard drive space. Its a problem of limited bandwith for miners. Miners are only capable of receiving so many transactions in a 10 minute period. if the total demand for transactions exceeds the bandwidth of your average miner than people will be forced into other chains.
Where do you get the idea that tx bandwidth is a major limitation? Most miners use pools, certain those bandwidth limited do.
100 tps (roughly 2x PayPal) * 400 bytes (average tx size) = 40 KBps. Yeah not GB/s or TB/s but KB/s. Now a miner will need to receive tx and send out the block and send to multiple peers but with the raw tx flow being 40 Kbps even a 10 Mbps connection provides sufficient headroom. Bandwidth for tx was never a critical resource. ByteCoin solves absolutely nothing. Under your scenario ByteCoin would work in conjunction with another chain so any full node is likely going to need to be a full node on both chains meaning bandwidth requirements equal the sum of tx flows on both chains.