If fatigue points are based on Con

[le Redoutable]

...
And Con is the stat for spellcasters,
Then
Spellcasters can marry spells with fatigue points expenditure
!!

 

[le Redoutable]

Just a reminder:
Con+STR ===> Elementalist ( alteration, evocation, invocation )
Con+Dex ===> Bard ( enchantment , charm )
Con+Int ===> Illusionist ( illusions, phantasm )
Con+Cha ===> Cleric ( abjuration, divination, necromancy )
Con+Wis ===> Druid ( conjuration, summoning )

 

[Argyle King]

...
And Con is the stat for spellcasters,
Then
Spellcasters can marry spells with fatigue points expenditure
!!

That's how casting spells works in GURPs.

They are powered by Fatigue Points