PHP modifying the underlying code

I have some questions for you about modifying some of the code/PHP of this theme.

The first, and most important, question is would you be OK with this? What I would like to do it reduce some of the PHP and database calls and replace them with static code that applies to my site. An example might be removing or commenting out the code for SEO plugin checks. This runs through several if statements, PHP calls and database calls for something I know I want off on my site.

The ultimate goal is to reduce the size of my site and increase its load speed.

Obviously if I started modifying this code I wouldn't expect you to support me if I ran into issues. My second question would be how would modifications such as that affect theme upgrades in the future? I'm new to the theme so I haven't had to upgrade the code yet but for example if I did comment out the code for SEO plugin checks and just default it to OFF would I have to redo that when the next upgrade comes out?

Thanks,

Mark