To the people saying he should have come with TR Voyager Optimus' weapons: Wow, you're right, it totally makes no sense that Hasbro didn't include the weapons from
a completely different figure with a completely different set of molds - Oh, wait a minute, yes it does.
Now that that's off my chest...
I'm pretty sure I know why he comes with no armament other than the bucklers/combiner feet.
For those who are unaware, Hasbro has a very rigid size class/price point system. They impose a strict upper budget limit on how many grams of plastic, how many ounces of paint, etc. are allowed for figures of each size class in each line to ensure they have the same price (which drives some of Takara's designers bonkers at times). So I would presume that Grimlock's bulk took up the rest of the plastic allotted to him. Annoying, but at least I understand why it happened. And I'm overall happy with Grimlock otherwise - it's a little disappointing that he's not taller, but still. He's got good poseability and the combiner torso mode is well done in my opinion (the leg setup works better on him than Motormaster's attempt at it, and the ankle rockers of the PotP combiner feet take care of any remaining problem potential I think.
I would like to point out that Titans Return and Power of the Primes do provide quite the selection of separate weapons, so there is that, though none of them are direct matches.
Nonnef is probably the best bet as far as 3P weapons for him, they've done good work so far.
Of course, if you happen to own G1 Grimlock's accessories, here's a fun fact: They're double-posted - the pegs actually have a 5mm upper section.

Admittedly, the sword looks a bit undersize in his hand, but still.
Bradimus, retooling CW Hot Spot into RiD Prime was highly unlikely for Power of the Primes. RiD Prime is not a G1/IDW character. That kind of thing is more the purview of E-Hobby and TakaraTomy Mall exclusives.