Hello,
I recently started working in a state government project that is being built from the ground up. I was brought in by the communication team to champion user experience in the technology platform the project is building but have been struggling to truly find my place.
The project has people responsible for different aspects of user experience:
• There is a team responsible for designing business processes, which also does user research and persona development.
• The communications team is out in the field talking to real users.
• There is someone conducting user testing and usability.
• I am responsible (for now) for copy and content.
• And many many developers, mostly contractors (if that is relevant)
The problem is that no one thinks of all this as one process and the gears are not really working together. Leadership is mostly developer-focused, and it is the developer-team leads who make many UX decisions during sprint.
They send mostly finished screens to me for “grammar review”. The result is a lot of re-work, or problems being surfaced after it is too late to make changes or tasks being delayed because solutioning was not complete.
We are now wrapping up the first phase of the project and moving into another. There is a window of opportunity to create better processes and leadership is interested in that.
I want to suggest to leadership that we need more focus on upfront designs and that we should move wireframing and copy before sprint, when there is enough time for feedback and iterations (Duh, I know).
How do I sell this to stakeholders without alienating other teams, or making them feel I am crossing swimming lanes? What else should I be thinking about?
Welcome. 
The tricky thing here (in my experience) is often coming in as the new guy and introducing change. People can get their backs up and then the whole process becomes fraught. Is there someone that has been around for a while that you trust? I’d start by getting their buy in so that they can support you and champion the message.
Seconding what @hawk’s saying. I’ve been in a similar position in the past, and did cross lanes to get colleagues on board for more collaborative work… writers, designers, analysts, marketing, sales teams, and developers… and it took years (seriously). The most effective way to influence process change was to get a single stakeholder on the same page and rely on them to slowly turn the ship around.
For your immediate issue of not having time in a sprint… one thing that started to work for our team was to make sure we had a loose roadmap that extended beyond individual sprints. It wasn’t set in stone… and emphasized some broad themes that focused on the users and connected that to organizational priorities (e.g., “Reduce the amount of time it takes a customer to check out”). In the end it was absolutely critical. This allowed designers/writers/analysts to always be working at least one sprint ahead (sometimes more), so design and copy would be in a workable place before development started.
We also asked to get some flexible time with the development team blocked off in every sprint. It didn’t have to be much, and sometimes we didn’t need to use the time… but it was important to have available. This allowed us to also collaborate with the development team, so they could have input on the design/wireframes/content that they’d be implementing in future sprints (this is much different than sprint planning and other agile artifacts!). The goal was to make sure everyone was involved, could give feedback, and make sure every part of the process was well-informed.
This shifted much of the time spent on re-work to pre-work, and it can’t be emphasized enough how much better it feels to be heading a unified direction rather than struggling to get changes in after work has already been done. And the work was better because it had a variety of perspective and input from the start!
I’ve heard a lot of teams say that they’ll make the changes in phase 2 of a specific project/feature… and the running joke of course is that phase 2 just never happens.
Good luck!