For peaches: chop and sprinkle with 2 Tablespoons sugar and 1 Tablespoon lemon juice. Let sit for 2 hours, or overnight in refrigerator. Purée half of the peaches with immersion blender and dice remaining peaches. Set both aside.
For ice cream: In a bowl, stir together 1/4 cup milk and the cornstarch; set slurry aside. Cut kernels off cob of corn and cut cob into large chunks; reserve kernels and cob together. In a 4-qt. saucepan, whisk together remaining milk and the cream, sugar, syrup, and salt; add corn kernels and cob and bring to a boil over medium-high heat. Cook for 4 minutes; stir in slurry. Return to a boil and cook, stirring, until thickened, about 2 minutes. Pour mixture through a fine strainer into a bowl and set 3 T of kernels aside.
Place cream cheese in a bowl and pour in 1/4 cup hot milk mixture; whisk until smooth. Then whisk in remaining milk mixture. Pour mixture into a plastic bag; seal, and submerge in a bowl of ice water until chilled. Pour mixture into an ice cream maker; process according to manufacturer’s instructions. With about 5 minutes left on the churning time, add in diced peaches & kernels.
In a loaf pan lined with plastic wrap, pour half of ice cream in. Then pour pureed peaches in layer on top and swirl, then remaining ice cream. Freeze until firm.