There are two elephants in the room to address here.
First, Lonnie is one heck of a large pile of soak. For the cost of a resource, you can heal one damage and one horror every round. The resources aren't hard to come by, and she's also a level 0, 5 health/sanity ally who says +1 in her card text, so you aren't even feeling like you're 'wasting' your ally slot for defense. Compare her to equally costed Beat Cop with one fewer sanity and an ability that you really hope you don't have to use! Lonnie can also provide the health healing for your fellow investigators provided they bring their own items for soaking damage. Also, note that 'choosing' is part of the ability and the lack of 'must' and 'then' in her ability text. If you just need the horror, it is totally legal to choose an item without damage - or even activate the ability with no available item at all.
Second, Lonnie isn't a mechanic. She's a tailor! She doesn't fix motorcycles and cars - she fixes shirts. AHCG has a small selection of items with health, mostly 2 health: Leather Coat, Trench Coat, Leather Jacket, and Robes of Endless Night
Will we one day see Motorcycles as player cards? I hope so and expect it. The motorcycle is one of the most iconic cards from Arkham Horror, and both Tommy Muldoon and Daniela Reyes are big fans of them! Plus, it is confirmed that we will be seeing the new Vehicle trait in The Innsmouth Conspiracy, but the couple of revealed spoilers have shown scenario specific assets without health stats.
But until then, Lonnie is stuck mending coats, jackets, and dresses!