[DF] Imma Chargin' Mah (Fantasy) Lazors!!!

[Jovus]

How can I get in this game? (Kidding, but it would be cool.)

Were I you, I'd also look into secret spells and strange ways to interact with or use current spells for a SF feel. Things that come to mind immediately are Force Dome as force fields (complete with magical/material ways to bypass or "overload" them) and manaburner engines powering rickety TL 4^ vehicles and establishments held together with Essential Wood or Earth. I'd imagine you don't want to go overboard with this, though.

Places to look for direct inspiration might include GURPS Technomancer, though that's a higher TL than you intend, and GURPS Fantasy Tech 1 - The Edge of Reality (I don't think there are any more in that series, unfortunately.)

Also, it needs be said that much of the magic in Jack Vance's Dying Earth books has the feel of actually being science. D&D magic wands have always (to me) had the feel of being ray-guns and the like, complete with limited charges and strange methods of activation.