That's what fender flares are for (or poke) I'm not worried about anything rubbing, when you buy adapters you can get different MM thickness plus you can get pretty much and offset you want with wheels. But I looked up an 08 smart car dimensions 11" in front 8" back. Everything should clear fine.
The issue is, still, that you have to clear the calipers with the barrel of your wheel, so if you went with a 25 mm spacer that allows you to bolt on a 4-hole wheel, but then get a wheel with 25 mm more negative offset to offset the spacer, then the rim is still in the same location and needs to clear the caliper.
There are some alloy wheels that have more clearance for their tire size dimension, but those tend to be really expensive (but also very light). That's due to the fact that having a deeper barrel creates a stronger and/or stiffer wheel just from the shape. A lighter wheel with the same stiffness or strength is going to have to be made using more expensive manufacturing processes or materials.
Steel rims don't have this same problem and it's likely that a 14" steel rim will clear the caliper on the front.
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