Since the SM3 set has been fully revealed, I decided to build a Ho-oh GX deck with Kiawe. I made some proxies and sleeved them up. In short, this has potential. This is a rough list, so it will need work. This deck is built with the upcoming rotation in mind, so I don't play Shaymin EX or VS Seeker.
Deck
Pokemon 9
4 Ho-oh GX
3 Tapu Lele GX
2 Turtonator GX
Trainers
4 Sycamore
4 N
4 Guzma
2 Kiawe
2 Pokemon Ranger
2 Hex Maniac
4 Ultra Ball
4 Max Elixir
4 Choice Band
2 Field Blower
1 Switch
3 Scorched Earth
Energy 15
15 Fire
Strategy
Power up Ho-oh GX early with Kiawe and Choice Band to swing for 210. Utilize cards like Guzma and Pokemon Ranger to circumvent the downside of Phoenix Burn. When Ho-oh GX goes down, use Turtonator to set up another Ho-oh and continue blasting.
Key cards:
Ho-oh GX: Our main attacker. Phoenix burn does 180 for 4 with the downside of not being able to use Phoenix Burn next turn. Attach a Choice Band, and we are OHKOing everything that currently sees play in the meta, aside for the occasional Vikavolt GX. Sacred Fire is a nice mop up/set up attack for things that are just out of reach.
Turtonator GX: Backup attacker and our "reset button" when Ho-oh goes down. Nitro Tank GX is our GX attack of choice.
Guzma: Guzma is amazing in this deck. Often times after a KO, your opponent will give you a non-GX/EX to deal with. You can play Guzma to pull up a valuable target and bench Ho-oh, resetting Phoenix Burn. If you have a Lele active, all you need is one energy and you can retreat back into Ho-oh.
Kiawe: 4 energy is too expensive. Kiawe fixes that. Even if you don't manage it on your first turn, Kiawe is still useful on turns that you wouldn't be able to attack anyway. I generally only use one per game, but you want to make sure you don't prize it, so play at least 2.
Pokemon Ranger: For those times when you need to Phoenix Burn the active, even though you just used it last turn.
Hex Maniac: Stop non-GX Alolan Ninetales and Araquanid from walling you.
Choice Band: 180 isn't always enough. 210 usually is.
Scorched Earth: Draw support and a counter stadium. Altar of the Sunne isn't reliable with Field Blower in format and I can't think of a better stadium to play here.
15 Fire: I want to make sure I can hit my Max Elixirs as much as possible, even after a Kiawe. If you want to make space for other cards, I'd suggest looking here first, but know that your Max Elixirs will be much worse.
Non-inclusions:
Volcanion EX: Not necessary and a huge liability. He also clogs up the bench.
Baby Volcanion: Turtonator and Kiawe do his job better.
More item based switch: Garbodor is a problem and I don't want to feed the trash monster. Also, with Lele having a 1 retreat cost and there being 15 energy in this deck, the double swap via Guzma isn't hard to pull off.
Deck
Pokemon 9
4 Ho-oh GX
3 Tapu Lele GX
2 Turtonator GX
Trainers
4 Sycamore
4 N
4 Guzma
2 Kiawe
2 Pokemon Ranger
2 Hex Maniac
4 Ultra Ball
4 Max Elixir
4 Choice Band
2 Field Blower
1 Switch
3 Scorched Earth
Energy 15
15 Fire
Strategy
Power up Ho-oh GX early with Kiawe and Choice Band to swing for 210. Utilize cards like Guzma and Pokemon Ranger to circumvent the downside of Phoenix Burn. When Ho-oh GX goes down, use Turtonator to set up another Ho-oh and continue blasting.
Key cards:
Ho-oh GX: Our main attacker. Phoenix burn does 180 for 4 with the downside of not being able to use Phoenix Burn next turn. Attach a Choice Band, and we are OHKOing everything that currently sees play in the meta, aside for the occasional Vikavolt GX. Sacred Fire is a nice mop up/set up attack for things that are just out of reach.
Turtonator GX: Backup attacker and our "reset button" when Ho-oh goes down. Nitro Tank GX is our GX attack of choice.
Guzma: Guzma is amazing in this deck. Often times after a KO, your opponent will give you a non-GX/EX to deal with. You can play Guzma to pull up a valuable target and bench Ho-oh, resetting Phoenix Burn. If you have a Lele active, all you need is one energy and you can retreat back into Ho-oh.
Kiawe: 4 energy is too expensive. Kiawe fixes that. Even if you don't manage it on your first turn, Kiawe is still useful on turns that you wouldn't be able to attack anyway. I generally only use one per game, but you want to make sure you don't prize it, so play at least 2.
Pokemon Ranger: For those times when you need to Phoenix Burn the active, even though you just used it last turn.
Hex Maniac: Stop non-GX Alolan Ninetales and Araquanid from walling you.
Choice Band: 180 isn't always enough. 210 usually is.
Scorched Earth: Draw support and a counter stadium. Altar of the Sunne isn't reliable with Field Blower in format and I can't think of a better stadium to play here.
15 Fire: I want to make sure I can hit my Max Elixirs as much as possible, even after a Kiawe. If you want to make space for other cards, I'd suggest looking here first, but know that your Max Elixirs will be much worse.
Non-inclusions:
Volcanion EX: Not necessary and a huge liability. He also clogs up the bench.
Baby Volcanion: Turtonator and Kiawe do his job better.
More item based switch: Garbodor is a problem and I don't want to feed the trash monster. Also, with Lele having a 1 retreat cost and there being 15 energy in this deck, the double swap via Guzma isn't hard to pull off.