I'm intrigued by the possibility of applying osTicket to a couple of small business I'm involved with. However, it is missing a key feature I've used from commercial help desk software. Specifically, the ability for an agent to reply to a ticket via an email (reply to an assignment or new ticket notification). I won't go into all the use cases right now, but since I've seen this feature requested by others, but objections have been raised. I'd like to try to address the most common objection I've seen which is ticket locking, or avoiding agent collision.
I've worked for decades on both small and large (thousands of seat) commercial customer support systems, many without any ticket locking! All of those systems use ticket assignment rather than locking as a way to avoid agents stepping on each other. But, by design, they do not preclude multiple agents working on the same ticket. I've seen this "optimistic concurrency" model work well very large contact centers and very small contact centers.
My suggestion for a feature like this is to not worry about locking. Instead focus on how agent assignment can address concurrency concerns. A couple ways of doing this might be a) agent reply by email only works if the ticket is already assigned to agent, otherwise the reply becomes a private note essentially to the agent that 'owns' the ticket. And b) if the agent isn't assigned an agent reply to the ticket could auto-assign the ticket to that agent. Both of these options should be optional and enabled through configuration