I like the talent idea, but frankly I'd just make it apply to the first spell the caster is attempting to sustain rather than a specific spell type. They're still spending strain if they need to move and act.

I don't remember who suggested it on the forums, but one person came up with simply bumping the difficulty by 1 for a spell to extend its duration to a scene.

Or perhaps simply allowing two advantage or a triumph to "anchor" a spell for the remainder of the scene. Personally "for a scene" is far better than "for X turns" because there's no bookkeeping, and if fights are typically only a few turns, there's no functional difference. Spending advantage on concentration means not using it to recover strain, so it still carries a cost.

I still can't shake the feeling that too much of "classic" RPG spellcasting gets discouraged by the "concentrate or it goes away next turn" default of Genesys, and Doughnut's reply just reinforces this.

I'm surprised the strain cost is that much of an issue. Most combats I have ran don't last long enough to warrant the need to maintain more than a spell or 2. The maneuver limitation seems to maintain a good balance that keeps casters from gaining too much of an advantage from stacking spells. Creating talents to help enhance spellcasting could also help in this area, here are some examples:

Blood Magic Novice
Tier: 1
Activation: Active (Incidental)
Ranked: No
Once per round during your character's turn, when your character would suffer strain from using the Concentrate maneuver, the character instead suffers 1 wound.

Arcane Extension
Tier: 3
Activation: Passive
Ranked: Yes
When you purchase this talent for your character, select one magic action (spell). Your character does not suffer strain when performing the Concentrate maneuver while sustaining a spell chosen by this talent.
Each additional time you purchase this talent for your character, select a different magic action which gains the same benefit.

Stupendous Concentration
Tier: 4
Activation:
Ranked: No
Once per encounter, you may spend a Story Point to use this talent to prevent your character from suffering any penalties while casting spells this turn. Additionally, your character may automatically maintain any spells until the end of their next turn without needing to perform the Concentrate maneuver.

Well, there’s also casting in preparation for a battle...

I plan on usin this talent for extending spells in the basic magic system:

Extend Spell

Tier: 1

Activation: Active (Incidental)

Ranked: Yes

Your character must have purchased a magic skill to benefit from this talent. When using the concentrate maneuver (see page 218), you can choose to extend one magic effect as incidental action instead of a maneuver in each encounter. The effect is extended as an incidental action for one turn per rank. You cannot have more than one extended spell effect at a time, but you can still use the concentrate maneuver to extend other spell effects. After the effect of Extend Spell ends, you can still choose to continue extending the spell using the concentrate maneuver.

You should use this talent in all settings that include magic skills.

8 hours ago, Doughnut said:

One of my group members who is our other main GM is talking about running a medium fantasy game and we've been talking about making a talent or two to enhance concentration. Note these are all still in the high planning stages, not ready for implementation, just ideas.

You could look to the Druidic Circlet for ideas on restricting enhanced concentration to very specific spells. Also the two necromancy NPC’s in FFG’s GenCon adventure have ideas to draw upon.

I wanted something like an extension to the Signature Spell concept.