River gunboats

[The Rock Doctor]

The Union invested a decent chunk of change in river gunboats for operations in Europe back in the 1890s and 1900s.  They were, of course, a relatively fast way to move firepower along rivers, to secure said rivers for one's own use and to deny their use to the enemy - the Northern Kingdom, the Golden Horde and the Romans being the three largest neighbours for whom there were probably worries about a general European land war.

But now we're in the 1920s and we've got tanks and airplanes providing faster and cheaper firepower across battlefields.  Does it make sense to field 12-knot gunboats that will be outnumbered and out-maneuvered from land and air?  Are river monitors now only suited to colonial environments where the threat level is somewhat lower?

In short, do I replace obsolete units or assign resources elsewhere?

What say ye?

[Kaiser Kirk]

Tanks at this point are weakly armed and armored, and self propelled artillery is quite slow and typically heavy howitzers.
The majority of artillery is horse drawn and kept under ~1000lbs/500kg so it is crew-pushable. QF 75s and similar are low
velocity and at worst would have solid shot.

A vessel that can move long distance/day, With a ~100mm HV gun, a company's worth of MGs, and an inch of armor plate,
that would be a real threat to any pontoon bridge effort, ferry crossing, etc.   Likewise it would aid in just such an endeavor.
Now in the abstraction of our land combat, a single vessel would simply disturb timelines. A flotilla though could buy a month or
impact supplies. The reality is that 1BP spent on 4 Gunboats will not be as cost effective as 1 BP spent on an LP or AP....
I have a feeling the latter are far to 'cheap'.

In riverine service elsewhere they make great storyline sense.

So IMHO, I see a role for limited numbers that don't eat up to much budget.
Currently I've settled for refurbishing my old existing ones, building a lot of littoral aux gunboats for that storyline role,
and I keep designing Gunboats with best intention of building swarms...