Gotta have a more realistic question though: Shirou is a pretty bad mage, but EXTRA and FGO implies the average person has overall better circuits even if he will also nerf a servant in some shape or form.
But Shirou could fuck mana into Saber - a practice that should be all-around effective considering in the Fate route while Ilya is originally puzzled how Saber had recovered she quickly connected the dots in disgust that they had done a sex mana transfer in her proprerty.
And Arthuria could fire at least:
>the Caliburn that Shirou projected against Hercules
>Excalibur against Gilgamesh
>Excalibur against Gilgamesh, again
Before needing to have recharge sex.

So couldn't most issues of summoning a high drain servant or something like a Berserker be solved if you just fucked your servant periodically? A cumshot empowering the name release of a goddamn Anti-Fortress Noble Phantasm twice is a LOT of power.