Can retail traders trade directly through exchanges?
No, they can’t. All trades have to be routed through brokerages. For more information, read this post on NSE’s website. Why? Brokers are a key layer between exchanges and traders. They exist to offer technology, back-end support, settlements, manage complex compliances, provide financial assistance and take the financial risk on behalf of the clients, thereby creating a layer of comfort and safety for MIIs to focus on their core activities. Without them, managing the transaction, funds, support, and various other small requirements of traders/investors are practically impossible.
Does this mean it’ll never be possible in the future? Never say never because anything is possible, but it is likely to create massive bottlenecks given the current structure, which can result in undesirable consequences.