The market is the biggest problem - mechanics probably don't have a decent internet connection at work to start with, don't want to learn new software, and wouldn't even think to look for new software.
How many mechanics have email ? I think a large percentage.
How many people starting up new mechanic businesses are in their 30s or even 20s and reasonably net savvy ? I imagine quite a few.
Course these questions are best answered with some research and discussion with mechanics.