So again I ask, "What exactly is the upgrade?" Looking at the photos, the bread makes the sandwich look thick, but you don't see much in between those slices; maybe a bit of lettuce, perhaps a hint of tomato or peppers, and is that brownish color the meat? Maybe the BLT is upgraded because cheese is now incorporated, but you cannot upgrade a Philly Cheesesteak by changing from a roll to sliced bread. That seems more like an insulting downgrade in my opinion.
The Grilled Cheese sandwich is an ultimate comfort food of its own. No matter what your age, toasted bread with gooey cheese brings out warm childhood memories, especially when it is nasty weather outside. When you add another ingredient inbetween the gooey cheese, isn't that an "upgrade" in itself? Consider the Tuna Melt or the Patty Melt; both made the same way as a grilled cheese, but with the inclusion of either tuna or a hamburger patty. What about when tomato and bacon are added to a grilled cheese? Just add lettuce and there's your BLT right there.
I'm also going to use mayonnaise as my frying oil, instead of traditional butter for a grilled cheese. If you're a fan of flavored mayonnaise such as avocado, wasabi, chipotle or sweet chili, spread those on the insides of your bread slices; use regular mayonnaise for the frying.
Time to make the sandwich...
Besides the mayonnaise, you'll need four slices of thick cut bacon (or double up with thin bacon), slices of tomato (2 to 3 depending on the size of the tomato) and Romaine lettuce (try to use the stems inside the head, they're crispier).
Slather mayonnaise on both sides of each slice of bread, don't be cheap about it! Heat your stovetop griddle or skillet on medium-high heat, place the slices down onto it and put one slice of American cheese, then cover that with a slice of Cheddar. The American will melt into ooey-gooeyness while the Cheddar will form an enclosure, or seal, to keep the cheese from oozing out.