Help with Di box functions

Hi All, I am planning a new youtube video featuring a DIY DI Box. I am using the Jensen Transformers Schematic, and modifying it a little.
I was hoping someone could help me decide if the following changes would be acceptable:
add a DPDT switch after J1 & adding a third jack for a stereo input that can be summed to mono through two 10k resistors before the C1&C2 network.
Also, I wish to remove S2, R1, & R2 (selectable -10/-20db pad) and replace with a 4.42k resistor for fixed -15db pad. I'll also omit S3 and C3.

I wish to have a flexible DI box that has dual inputs which can be mono summed properly. Thank you!