I know of some good folks who use mirrorless systems for video.... But I digress...
I think the issue is multi-fold.
1. Technical Aspect
- Are the current mirrorless systems sufficiently mature?
+ Are the available systems able to effectively capture the scene? (Speed of focusing, quality image processor, quality of image sensor at various ISO etc.)
+ Is the lens selection adequate?
+ Are the accessories adequate? (Flash, secondary media slot etc.)
- Assuming that the 35mm dSLR systems are the de facto leaders in this field, do mirrorless systems offer any benefits that 35mm dSLR systems cannot?
2. Client Acceptance
- Can the client(s) accept the use of a mirrorless systems?
+ Do they trust the skill and output of both the photographer and the latter's tools?
+ If "face" in important to the client, then what are the perceptions of the guests on the use of the mirrorless systems?
3. Business Solutioning
- What advantages do a mirrorless system provide over a traditional setup? (Cost? Strategic advantage?)
I think with these pointers as starting points, you will be able to discern if there is a market sufficiently large for the use of mirrorless systems today for important personal events such as weddings.
As with point #2, I was also trying to make an alternative point. And I think this trust may have nothing to do with the photographer's skill. True, we will call them the clueless ones, but clueless they shall be. Of course, I'm not saying to carry the top gears to shoot just to gain that trust, but I think as per breaking down of an issue and I think this is also one issue which may not be often, but also worth considering for the open-minded.