... what, god no.
The core power of Spirit is unleashing Silent Hill monsters on people like the world's most twisted Pokemon player. "I can't bind spirits or ghosts" is a crippling disadvantage.
Well, you can still have a fetish for binding Spirits, but you won't get a Fetish by Binding a Spirit with DimSci.
And yeah ideally you'd want to include some extra stuff like mucking with spirit-world physics and conjunctional Life/Mind rotes, but not being able to just randomly call up EDEs and command them to do Your Bidding Which Was What They Wanted To Do Anyway is a pretty hefty elimination of most of what Spirit does.
If you're importing the nMage system wholesale to cover magical effects then you won't have Dimensional Science as Sphere/Arcanum. Not unless you homebrew it in, which is a lot more work.
First, port over all the Spirit stuff that deals with reinforcing, weakening, crossing, or perceiving in relation to the Gauntlet, or to perceiving spirits or shielding against spirit powers. Include Harm Spirit and its expansions.
Include Shape Spirit as the "Cosmogenesis" equivalent. Note that once created, your DImensional Science will still not be able to bind or control it.
Include anything that involves manipulating the substance of the Shadow directly, such as Spirit Manse (i.e. "Create Horizon Realm").
Disclude anything that directly involves influencing Spirits in a non-phaser manner, apart from Shape Spirit. This will be most of the Sphercanum.
Declare that Dimensional Science as a whole treats ghosts as spirits. Consult someone you respect in matters of both oMage and nMage mechanical fudgery whether beings of the Astral should be affected in such a way.
That's the basic form.
You might also want to add stuff like being able to use DimSci/Mind to allow use of Mind on Spirits, or the same for LIfe. Also may want to include things like Format Space's control of dimensional properties.
... nah. Actually, nMage actually has Matter as Just Plain Better at that, because both Death 3 and Matter 3 can animate corpses (as corpses are also inanimate matter), but Matter 3 can also animate all kinds of other shit.
(the precedent is also set by this that you can probably animate a fire with Forces 3, and then use Mind to teach it Kung Fu and then go and use multi-attacks on vampires. And then you laugh)
Oh, well, even better then.