There is nothing wrong with spacers, but it just goes to show how much wheel you'll be able to run. The stock S197 fenders will support an 11" wide wheel with different offsets front and rear (fronts being about 25mm-30mm less aggressive than the rears). An 18x10.5 ET38 will fit at all four corners, with the rears poking slightly, and a 5mm spacer up front when combined with 315 wide tires front and rear.
With a wide body kit adding that much, no reason you shouldn't be able to run your 18x12.5's at all four corners if you wanted to, and 335's at all four.... I wouldn't recommend that wide for a DD as it will follow every rut in every road, but hey, some people are nuts!
I would like to at some point go with smaller tires because I found out that replacing 345x25x20s in the rear is not inexpensive.
I'm running 20-inch rims all the way around you keep mentioning 18's, so of course, that means springing for a new set of rims, which I would like to do at some point.
On that note though can I gather some more Fender clearance vertically by going to an 18-inch rim, even with adding some more sidewall on the tires, the 25s look great but they're awfully thin for DD.
Any advice on tire sizes that will give great handling but are on the more reasonable side of price because they're more used in the general population?
And if I want my tires to stay where they are, out towards the fender Edge, by going with a smaller Tire I'm guessing my spacers are going to have to increase in size otherwise the tires are going to look funny if they go too far in under the fender.