Likewise, the world does not revolve around freight operations.
Given that in
2022/2023 financial year [page 198/228] the entire freight industry paid a total of £11m (down from £53m the previous year) to Network Rail for infrastructure access, compared to well over £2bn for passenger operations..... I'm not sure crippling the Elizabeth Line for the marginal benefit of freight operators is a good plan given the dire financial condition the railway is in.
It's hard to get good data but I'd be very surprised if Elizabeth Line didn't pay far more than the entire railfreight industry for the upkeep of the infrastructure.
However, even if you were going to require additional infrastructure to allow freight operators to avoid shifting to night operations etc, the obvious answer would be to build a single track freight railway which could easily handle the required traffic. That would have the major advantage of ensuring that low performance freight trains stop getting in the way of passenger operations (of any type).