This is probably the dumbest suggestion to ever see the light of day. There's no nicer way to put it. Banning Chansey makes more sense. Banning Fearow, as was suggested in jest, makes more sense.
With that out of the way:
I. Economy
Talonflame has been gutted for a long time. Randomly increasing the value of a single Pokemon for no good reason (see later sections) would essentially be giving up on any sort of effective economy where value is persistent. When Talonflame was nerfed, everyone knew it was coming eventually. This is the equivalent of giving Kyurem (if it were tradable) (and likely now Garchomp as well) Dragon Dance from Generation 8, arbitrarily skyrocketing its value. This will be abused, no matter how vigilant moderation staff is.
II. Consistency
There are so many things that do not work properly on PRO, but most of the differences with Gen 7 standard mechanics are due to the game not being complete (missing Pokemon, moves) or bugs (U-Turn / Volt Switch). The only precedent for this kind of change is Tail Glow Phione, which was questionable in itself but largely ignored due to its uselesness.
III. Actual Effects on PvP
For reference, Talonflame sets will be listed here:
Talonflame @ Choice Band
Ability: Gale Wings
Adamant Nature
252 Atk / varying HP / varying Spe
- Flare Blitz
- Brave Bird
- U-Turn
- Roost / Will-o-Wisp / Steel Wing
Talonflame @ Sharp Beak
Ability: Gale Wings
Adamant Nature
252 Atk / varying HP / varying Spe
- Swords Dance
- Brave Bird
- Flare Blitz
- Roost
Talonflame @ Leftovers
Ability: Gale Wings
Careful Nature
varying HP / varying Atk / varying SpD / varying Spe
- Taunt
- Roost
- Brave Bird
- Bulk Up / Will-o-Wisp
This is a fundamentally polarizing Pokemon, and not one that allows for interesting developments in the metagame. Choice Band sets can invalidate current offensive builds on a whim, Swords Dance excels at shattering certain builds of Balance, and Taunt makes for an excellent stallbreaker. Much like Manaphy, which people continue complaining about to this day, Talonflame's list of true answers is short and often can be chipped out by status or hazards. Rotom-Wash and Tyranitar cannot take U-Turn forever, and incorrectly evaluating the set can have devastating effects - Tyranitar hit by Will-o-Wisp, Thunderbolt Clefable nailed by Choice Band Brave Bird.
While there is no doubt that Gale Wings Talonflame would not be broken, adding polarizing threats does not make a metagame more fun. We can see this both by looking at what Smogon bans and does not ban, as well as player opinion on PRO as a whole. Recently, Smogon banned Galar Darmanitan and the Dynamax mechanic at large. Galar Darmanitan has never had the presence of Landorus -T in previous generations of OU, so why was it so quickly sent off? While answers to Landorus-T generally come naturally in teambuilding Gen 7 OU, Galar Darmanitan is polarizing. It forces players to run soft checks such as Rotom formes, or subpar Pokemon in hopes to wall it. Talonflame is much the same - while sets like Defensive Garchomp and Defensive Rotom-Wash are strong and popular, they cannot reliably answer Talonflame alone, as it can defeat them over time.
Now, let's take a look at the archetypes PRO players love to complain about.
1. Rain
It's quite self-evident what rain teams do. You pack a Kingdra answer and a Manaphy answer or you lose. People hate this archetype.
2. Stall
Stall is hated because of its ability to drag out games which feel hopeless for the losing side. It's also more complicated to answer than Rain, but just as polarizing nonetheless.
Why combat this by bringing back a similarly polarizing and uninteractive Pokemon? There are plenty of more interesting options if bulky Balance truly needs a boost - Victini? Tornadus and Thundurus? Even Volcanion can make Balance's somewhat difficult Rain match-up much, much stronger.
Lastly, we've seen this all already. We know what Talonflame does. It would be better to bring in truly new Pokemon rather than unleash an old tyrant once again.
tl;dr: don't change Talonflame's value again; be consistent with Gen 7 as much as technical limitations allow, who the heck thinks Talonflame would be a positive influence on the metagame