Syr Gwyn looks interesting to me - the card draw ability promotes a go-wide strategy, while the equip 0 ability lets you play all sorts of beefy equipment. Keywords also provide support for an equipment-based voltron strategy. I would say the primary attraction of the commander is getting to play all sorts of equipment without needing to deal with equip costs - there are a lot of sweet pieces of equipment that I want to play but can't because they require too much investment, such as
Moonsilver Spear and
Argentum Armor.
There are some concerns though - costing six mana is certainly one of them, since if you're filling your deck with
Colossus Hammer and friends, then you may not be able to equip them until your commander is out. Deck needs to have a lot of ramp to play Syr Gwyn ahead of curve consistently.
The other major concern is Knights as a tribe - they're a bit one-dimensional, with the vast majority of them being french vanilla, combat-focused creatures. There aren't many knights that generate card advantage or provide interaction, so you'll need to lean pretty hard on your equipment for that (which, again, means that you need to have your commander out consistently).
...and of course, if you're filling your deck with Knights and Equipment, then that greatly limits how many slots you have available for removal, card draw, and ramp, which makes the deck even more one-dimensional.
...I think my primary concern is actually that most tuned Syr Gwyn will probably be a bit repetitive, playing the same set of knights and equipment. There aren't a lot of different directions it can be taken, and the pool of cards that synergize with the commander is a bit shallow. I generally prefer commanders that allow a bit more customization.
Zacama
