> simply
I honestly think anyone using the words "simply" or "just" doesn't know enough about a situation.
> ban Russian
Do you mean the nationality of the ship's flag state, owner, beneficiary owner, constructor, charterer, captain, any of the crew, the origin of any of its cargo?
I'm not an expert in shipping and I've probably missed a few other sources of nationality. The point I'd like to get across is that merchant ships are very international. Unlike warships, which are built, owned and operated by a specific nation's navy, there is rarely a specific nationality merchant ship.
If your nation bans merchant ships (based on some specific criteria), all it means is they get fewer goods by sea and they'll be more expensive.
A specific nation's maritime interests are chiefly that any merchant ships get to and from them, as well as their explicit warships having passage.
This issue is about cable damage by the Chinese-owned, currently (but not formerly) Chinese-flagged, Chinese-built, Chinese-captained merchant ship the Yi Peng 3. Some nations accuse it of committing sabotage, for which they don't have hard evidence, and they don't accuse China, they accuse Russia, and they claim that somehow the evil Russians influenced the Chinese captain, or one of the crew, to drag their anchor on the seabed. But only after they departed a Russian port... even though these nations' evidence is supposedly encrypted transmissions between the ship and Russia, which could also have been sent before docking in Russia... or even sent to any ship in the area, including ones not docking in Russia. Any nation can send messages to any ship, regardless of who owns, runs or hires it.
> or Russian-originating ships
Do you mean a full naval blockade of Kaliningrad and Leningrad oblasts? By who? All of Denmark, Germany, Poland, Lithuania, Latvia, Estonia, Sweden and Finland? That'd be enormous, hard to enforce, and would almost certainly be taken as a declaration of war.
Or were you imagining just a blockade of the Baltic Straits by Denmark, in violation of the Copenhagen Convention of 1857? The last time the straits were shut was by the Nazis when they occupied Denmark, because they were at war with most other nations.
Or do you mean, by "Russian-originating", any ship that has docked at any Russian port in its recent history? Merchant shipping is the Amazon delivery of the sea, they just keep going, taking on cargo and offloading it in different countries on the most cost-effective route possible.
> set some standards for crew training and expertise
Already exists: the https://en.wikipedia.org/wiki/STCW_Convention
> Inspect them at the very least
Already the power and duty of harbourmasters, and a ship can already be stopped or escorted by a nation's navy if it's in their exclusive economic area or territorial waters.