I would classify Boswell’s Northwoods, Countryside, and Military Force as crossovers, and they’re pretty darn good. Countryside is the most obviously topped with notes of Vanilla and Caramel, followed by Northwoods with a much lighter application of Vanilla, and then MilForce, which has a slight off-dry pine thing going on. They’re delicious.
I also enjoy Sutliff’s Count Pulaski, a crossover English with the slightest sweet and anise topping - nowhere near what you get with Mixture 79 or even SWRA, but a very pleasant “something” that sits atop a really nice tobacco blend.
The challenge is that I haven’t discovered a crossover with “strength” as the target market for these types of blends appears to be the type of smoker who is coming from aromatics and dipping their toe in to the English world, so they’re not necessarily smoking for strength but for flavor. If you want to add a little strength you can always blend in some Five Brothers (fairly neutral addition) or even some C&D Big n’ Burley (which will definitely change the flavor of the base blend but might well work if you’re deft).