I prefer keeping a Spouse stock, even if using one off-road. I say get what you want from the start, and perform maintenance regularly. Modifications may look nice, but can be costly, and can create more grief than they're worth.
Whatever the tax implications, an older, poorly maintained, modified model may not compare well with a new one in stock form. Maybe modifications are better done on a Lease, since you can always opt out if the end result is unsatisfactory. Better that if you like to always have a new one; maintaining two never seems to work out.