Sledgehammer for the wrong nut
As others have pointed out, the only problem is with postal voting.
There are many checks around the system, and the parties are generally very relaxed about it the way it is.
BUT - postal voting is entirely different. There is really no scrutiny from the political party system around postal votes. There are so many loopholes.
Apocryphal stories abound about nursing homes etc, where bundles of postal votes are filled out wholesale by the manager with no oversight.
There are recorded examples of areas with large military bases where the voting register swelled by thousands in the runup to an election or referendum.
One serious problem from my POV concerns the counting of postal votes. In polling booth scenario, there is a register of voters which gives numbers of actual voters at any station, which is compared to the numbers of ballot papers in the box. This count is overseen by reps from all the parties. Pretty transparent and a lot of work for anyone to corrupt.
However the postal votes are dealt with by council workers away from the count. With the percentage of postal votes now being very high, that is a huge problem area for satisfying democratic concerns.