Can I switch the hot and cold water supply to improve the pressure of hot?
Your question boils down to &quot;please validate my wonky idea&quot; and I will absolutely NOT.
Yes, you can do it but you shouldn't. At best your proposal is something that would be done in a super emergency situation.

You can switch the hot and cold lines at the tank but that would really be quite an obtuse solution. So now your cold valve gives hot water and the hot valve gives cold water? Good luck getting the proper temperature from your shower if you have an anti-scald valve installed.
Sounds like a surefire way to deter the average buyers and lower your home's value.
I think you will find that by the time you've acquired the right tools to perform a wonky cutover then the cost of materials to just do things properly is insignificant.
PEX has made plumbing so easy that it's almost hard to screw up.