We deal with this issue at The Economist and in the past couple years, we've been able to implement some lean thinking to move things along faster.

At the core, what you're trying to change is the culture.

Culture has 4 components that a group of people (people in your org) share:
1. Value system (what they consider important)
2. Belief system (how the believe things work)
3. Behavior (habits, rituals)
4. Artifacts (manifestation of the above)

You need to start addressing the first 2, then you'll see the progress (or lack thereof) in the last 2.

Here's an example: a bad approval process that makes product development move really slow. We discovered this happen because the stakeholders want to show that they're contributing to the project. Because of this, they want to make sure they get to review the project and give feedback. This way, they can show their contribution for the product's success and this would be good for their performance review.

From this example, the value for these stakeholders is recognition. Their belief : giving feedback (even if it's superficial and immaterial) shows that they're contributing. The behavior: blocking process in order to get a chance to give feedback. The artifact: feedback for the product in email, request to do reviews, meeting invites.

How to start:
1. Find your allies. These are people who also want to move faster. Ideally people who work in your team
2. Show real value. The reason why you want to work fast like a startup is so you can deliver value to your customers faster and more often. What can you do to give other people around you (who you want to influence) a taste of what that's like? One thing that we did was to do rapid prototyping (without code) and do usability test, then shared the video highlights with the stakeholders.

I'll be happy to share with you the way we did this at The Economist mobile team and offer some actionable ideas to help you move forward with the transformation.

The best way to get in is to offer what they you know they need.

Try contacting accelerators/incubators and offer free/discounted accounting service for their startups if that's what you can leverage to get in.

Another way is to just go to startup events to find out what the needs are (i.e. you keep hearing the need for UX design), then figure out a way to develop the capability to offer that.

I don't understand the last bit of your question "so reviews can't be used", so I'll answer the first bit about building trust.

For the to-be-married couples, trusting who will come to their wedding is really important because of the potential risk associated with having their event ruined by "bad guests".

Building trust = reducing that risk.

How? Couple ideas:
1. Require the guests to link their social media presence. It's functions like a background check. One filter that could be useful here is to only allow linking to accounts that are at least a year old (or whatever period you choose )

2. Video interviews could be a good way to build the rapport also

Beyond the trust building, you can also reduce the risk by doing things like the following:
1. Have the guests join only part of the festivity that are less risky (bachelor's party) but still part of the culture
2. Have them seated in an area that can be controlled
3. Make explicitly clear that if the guests do any disruptive behavior, they'll be removed from the event
4. Have a representative of your company be present at the wedding or stand-by in case problem arises

Hope this helps.