A few offerings,
First off, I don't really like whistle tips, from eGo-T's, (both reg. & mega) Vision style, & the Mega Atty Whistle tip, they have never been anything but condensation traps for me. Removing the baffle on the inside will do nothing to stop that. Pulling from a chamber and tunneling it into a smaller space just creates this trap. Making a whistle tip smaller will cause it to trap more vapor condensation. The only way to get some consistency with them in my experience is to take a long, slow draw to prevent trapping vapor at the choke point that is formed by the whistle tip design. Make the plug seals a standalone item & offer a whistle tip as an option for those that prefer them.
On drip tips, I don't believe you can say that any drip tip is standard, the only dimension they follow is the outside diameter that will fit into an atty or cartomizer, and you never know what atty or cartomizer they used for that dimension. This is why every manufacturer's drip tip that can fit a 510 atty gets mass produced & becomes a 510 atty or carto drip tip. Length, style, & inside diameter will vary on all. Which is why some people prefer some tips to others. The GV Fluxos have a standard design profile, a drip tip, whistle tip, cap, etc., can be made just for them to work with the new cup seal. Length upon insertion, Fluxo inside diameter, bore thru hole diameter, (for best fit to seal over the nipple).
The plug seal only needs three tweaks IMO, one is to widen the slot cut for the wicks & is the one that should be done in a future revision, the second is to shorten the "nipple" on the inside that goes over the wick cup & is closest to the coil, this will give peace of mind that that "nipple" is not being burned by the coil & giving an odd or burnt taste. Don't eliminate it, just shorten it so it will still seal the wick cup from the main juice supply & prevent leakage in to the center air tube. Third & last is to slightly thicken the center main body of the seal by 5-10 thousandths of an inch. (Rough estimate.) This will make it more rigid inside the tube over the cup seal to prevent flexing, it will also take up any space or gap left when using various drip tips that may not fully compress the seal over the cup. As skinnee mentioned he uses the middle seal to take up the gap & would be a good way to judge how much thicker it needs to be.
I don't think the air tube needs to be enlarged, with the drip tips, caps I've tried, it works fine as is. Also leave the filling slots as is also, one of the whole points of this new plug seal was for easier filling & I don't think you can improve much more that what GV has offered for that solution.
All my 2¢