Oceanfaring Promotion - possible

I'm considering the addition of a possible promotion - oceanfaring.

Oceanfaring I - units that are restricted to coast tiles may move into ocean tiles
Oceanfaring II - +1 movement in ocean tiles
Oceanfaring III - +XX% defense in ocean tiles

Now II and III are similar to the guerilla and woodsman promotions, and so I see no problem implementing them; however, is Oceanfaring I possible? I mean, by using XML files and not going into Python?

I don't think the promotion would be unbalanced as I would only make it available with the same tech in which caravals are gained (I forget which one it is).

The Oceanfaring limitation is imposed in an XML line. Promotions are defined in XML lines. So you ought to be able to do what you want.

Btw, caravals require the Optics tech, but all tech requirements can also be editted in XML