can a world that has a full strangth Space Marine chapter with

the fortress of the salamanders can house most of the population of their planet during peak volcano season, so at least a few are certainly spacious enough to do so

the space marines wouldnt mind too much, as long as the guardsmen dont mess with their stuff

>>53228684
macragge does this splendidly

>>53228704
Came here to post this

Normally, worlds with sufficient population pay tithe to the Imperium in goods (manufactured, raw materials, anything they can provide that's useful) and men to the Imperial Guard.

Astartes, and the worlds they govern, generally do not pay any tithes, instead they fight. The resources of the world will be spent on maintaining the chapter instead. Essentially knighthood.

So it'd be very strange for any Imperial guard regiments to hail from an astartes-held world. But as messy as these things are, shared governance of a place or so doesn't seem impossible.

The marines may choose to raise regiments of planetary defence forces on the other hand, that may look and function much like any guard regiment, merely differencing in where they fit into the Imperium's organisation. And if their world is threatened by attack form a force they cannot repel on their own, then guard regiments could be deployed there to help protect the place. Possibly even being left there afterwards until they're a PDF force with a guard heritage.

>>53228684
>And if so how would this effect the both of them?
Jolly cooperation on the battlefields and promising guard recruits being taken by the marines

now what it is that you would want to do with them instead is a way more relevant question

>>53228684
If the population is big enough it should be possible.

The problem is the following:

The Chapter recruits are also the men best suited for the guard. Since many of the recruits die during training, there won't be too many fit young men left to join the guard and fight well. Probably only those who can't get geneseed implated at all. Since the military is normally better feed and healthier than the basic population, the genetic would drift towards more common geneseed mutation, making the planet useless for the Astrates

>>53228820
Promising boys join the astartes, promising girls join the guard...

>>53228820
System like Rynn's World can afford to support a chapter like the Crimson Fists and PDF that are in many repsects equal to Imperial Guard (the Rynnsguard). Now to be fair, the CF recruit from Rynns World and neighboring worlds but it kinda works.

>>53228747
>The marines may choose to raise regiments of planetary defence forces

A good example in the Dark Angel's books by Gav Thorpe where their recruiting world Piscina IV, owned totally by them (Azrael has to officially give it back to an Imperial Governer or something at the end of the trilogy) has a fully functioning PDF that basically wages a full on war on Orks kind of and rebels.

But given what >>53228747 said about how Regiments are raised, and given that I'm fairly certain a Chapter can't deploy commanding their own human IG assets, I have to assume that the PDF can't become fully mobilized.

Or some shit. It's vague.

Point is, if this question is about what I figure it's about: they're your dudes, go nuts.

>>53228889
Combine that with mandatory seed donation from the marines for IVF treatments of heroic guardswomen and presto, the population will naturally drift towards producing badasses.

>>53228684
White and Dark Consuls, its common for smurfs to interact and train guardsmen.