Yeah, weapons/accessories sets would be great... but would it be viable for Hasbro to do? I remember when Star Wars The Phantom Menace came out they released accessory sets for those toys, but I don't remember them ever doing it again for subsequent Star Wars series.

I honestly don't know if such an idea would be viable for Hasbro or not. It was something that was popular with action figures back in the 1960s with Captain Action. Would it be possible with Transformers? Seems popular enough for 3rd party makers aimed at adults with disposable incomes, but would kids buy it? I dunno. It sounds like a relatively inexpensive venture though if they wanted to try it. :/

But a safer option might just to stick to the universal 5mm post system and release accessories with other figures. e.g. Beast Hunters Voyager Ultra Magnus comes with the Forge of Solus Prime; which ought to be compatible with other Voyager Class figures like Optimus Prime and Megatron provided that they have 5mm post compatible fists. It would also help Hasbro sell those toys too. Imagine if a whole bunch of Voyager or Deluxe Class figures all came with a different Cybertronian Relic