Can an AKG mini wireless take the place of a DI?
Kind of, sort of yes
....but it really depends on what you're trying to do. Like a direct box, the wireless will convert your basses signal to a low-impedance signal to send to the PA mixer. The manual
shows that it can be connected to a balanced (like a PA mixer) or unbalanced (bass amp) input.
The wireless shouldn't color your tone, so it will be the "dry" straight-to-the-mixer sound, and for many people that's fine.
I don't have any experience with multi-effects units for bass, but they look like a good way to experiment with different sounds without spending a grand on different single-use pedals. The downside is they are limited to their built in effects and setting up the presets requires some manual reading, knob twiddling and button pushing, but it's fun to learn that stuff, right?
The drum machine in the B2 is a great idea, it really helps your rhythm and feel to play along to a drum machine. <looks for drummers...>