The work /cost required for solutions is often higher then anticipated at quick glance for example the 365 3rd rail issue.Solutions only apply to other franchises. Amazing how often with SE things can't be done.
As stabling /depot space at SE is maxed out that need to be addressed properly as part of any rolling stock increase which isn't quick and need a proper long term franchise agreement or radical thinking for a direct award (i.e. some planning not an emergency DA).
SE needs a decent amount spending on it to make changes including on the revenue side by gating stations and collecting revenue.