All suggestions, all personal opinion - I'm not right, no one else is wrong..... I'll focus on MK, as it is in the highest level of distress....
First thing WDW needs to do is to take advantage of their existing technology.... the stuff they PAID for. Today? We have Magic Bands..... OK, they are not "Magic" - they are just secured links to a Database.
Step 1 - implement the equivalent of "TSA PRE", or "TSA CLEAR". Start pre-screening your guests. My wife and I would GLADLY provide pre-screening info. Surprise

- that MAGIC BAND (back end DB link) could deal with this. And the computer infrastructure has already been PAID for.
OR? WDW could spend millions on "screening gates". "WDW PRE" lanes could easily work at ALL parks.
Step 2 - MK specific....The WDW Ferry. Most common "local" entry point. Have you SEEN the Transportation Center? It's HUGE, and very empty. Just me - that's where I would put "local" Security gates. Beats trying to shove stuff between the MK "Real Entrance", and the LAKE. Backing people up into the WATER is really Bad Show.
Step 3 - and I hate this one. Disney Springs remains as a complete Security Risk. In the past? WDW has played games to minimize the risk. The GAMES must end....
The New DS BUS outbound lot MUST have a Security Entrance Point..... regular, and "WDW PRE" lanes. You will go through one, or the other.....
Again, All suggestions, all personal opinion- I'm not right, no one else is wrong. Disney really needs to take advantage of the technology they have already PAID for. To do so would make them no more "evil" than every airport in the US. PRE SCREEN. Let people choose to provide Data NOW, or Data at ENTRY.
Oh - side note for WDW..... yes, my wife and I WOULD pay for this.