I think so.
I don't have the rule book handy and I haven't played in years so please excuse me if I get anything wrong.
At it's core the system is roll a D10 and add the skill bonus, looking for target number.
As I say, you wouldn't need the magic rules. Just make all the PCs companions. Maybe give them a grog or 2 to run as well if you think they'll need some cannon fodder.
Where Ars Magica could be particularly useful is the rules for regios. A regio is a region of increased influence of one of the, erm, spheres (spheres is not the word used by the rules). There are 5 spheres: Magical, Divine, Infernal, Fey, and Science. Most of the world is a mix of all of these but there are areas where one dominates. A regio's strength is rated 1 - 10. A humble church might have a Divine regio of 1-2. St Pauls in Rome might have a regio of 9 or 10. A regio of 10 is (or effectively is) the relevant realm/dimension. Not all regios need to go up to 10.
You probably see where this is going.
One thing about regios that I found particularly appealing is that regio have layers, like an onion. You don't simply walk up to a regio 10 area and see a portal, you would simply see a church, (or St. Pauls.) The first layer is coterminous with this dimension. A character might wander through an area with a high regio and not even be aware of it. Or maybe they do just the right (wrong) thing, at just the right (wrong) moment, and step through to the next layer, vanishing from this dimension. You can have as many layers as you like between this world and the final destination.
As an example: a fey regio that is centred on a standing stone. This regio is part of this dimension; someone standing by the stone can see/effect and be seen/effected by someone standing outside the regio. The area around the stone is regio 2; fey related things (spells, a fey's magical might) got a +2 bonus. By walking widershins around the stone 3 times on a moonless night they enter the next layer, with a regio of 5. The character finds themself in a new place, a sunny field of flowers. There is no sign of the mundane world now, the character is in another (pocket) dimension. There's a trod (a fairy road) leading off into the distance. By following the trod the character comes to a familiar looking standing stone, but this time there is a dark opening in the earth beneath the stone. By crawling through the cave on their belly the character is able to reach the next layer of the regio. And so on.
Populate each layer with whatever helpers, guardians, puzzles, traps you desire. And of course you can make working out how to reach the next layer of the regio a mystery in itself.
