This argument amounts to basically nothing more than "It's possible for fraud to occur, therefore it occurred", which is a completely spurious leap of logic.
Admittedly I stated earlier that voter rolls may not be updated properly, which means mail-in ballots may be sent to dead people by accident. This doesn't prove that dead people voted, or even that every mail-in ballot was sent in. Again, another spurious leap of logic.
As for signature matching of ballots, I might be more inclined to agree to your claim that not having signature matching opens up the election to widespread voter fraud if there was actually any evidence that said fraud occurred in those states.
So let's see, how many states actually have signature matching? Well, according to Ballotpedia, there are 32. So 18 states don't have signature matching. Let's narrow it down a bit, otherwise we're gonna be here all day.
There are 12 states that Associated Press has labelled "swing states". Of those states, 7 of them (Arizona, Florida, Georgia, Michigan, Nevada, Ohio, Texas) have signature matching and 5 of them (Iowa, New Hampshire, North Carolina, Pennsylvania, Wisconsin) don't. Let's narrow it down even further.
Of the swing states, the Trump campaign has filed lawsuits in 6 states. Of these, Arizona, Georgia, Michigan and Nevada have signature matching, which leaves only Pennsylvania and Wisconsin to consider, so let's examine those two states.
Neither Pennsylvania nor Wisconsin have automatically sent out mail-in ballots to every registered voter; you had to request an absentee or mail-in ballot, although Wisconsin did send out applications. So your erroneous voter roll claim doesn't apply here for those states.
Pennsylvania requires as identification the applicant's driver's license number or ID number, or the last four digits of their Social Security Number, as well as a signature on the declaration field. If they don't have any of those, they have to provide a photocopy of a valid ID. Wisconsin requires a photocopy of a valid ID. In order for widespread voter fraud to occur in those two states, there would also have to be identity theft on a massive scale.
As I explained in a comment on someone else's meme, in this country there is law known as "innocent until proven guilty". The burden of proof lies on the accuser, not the accused, to provide evidence of wrongdoing, and NO EVIDENCE HAS SO FAR BEEN PRESENTED. Why is this so hard for the Cult of Trump to understand?