Does Creveld say that? I have the book and I don't recall him making such a sweeping statement. He emphasizes that armies needed to keep moving, but that's not the same thing. Yes, desertion would be easier closer to home, but deserters had greater reason to leave the more tenuous the army's survival was.
You're right about the sutlers, for some campaigns -- although in many cases, unless you're organizing markets where farmers voluntarily come, a promissory note is little better than pillage with a receipt. And there are cases of Louis XIV's armies simply pillaging their own territory even in peacetime.
But at any rate, whether you buy food from willing sellers or force them to give it up, it's always going to be easier in friendly territory. No army is going to starve when there's grain in civilian barns nearby, regardless of their relationship to the owner.
These cases are the celebrated exceptions, and the three most famous ones -- Crecy, Poitiers and Agincourt -- all happened after a long chase through the larger side's territory and several operational errors by the smaller side, to my recollection.
I should add another reason to give provinces some ability to defeat or attrit invading armies, buff the defense, and make it more difficult to hunt down and intercept armies: Right now, the best military strategy in the same is to track down and destroy the enemy army, then carpet-siege -- lots of small sieges simultaneously. I can't think of a single historical campaign that fits this picture.
Remember in this era, battle deaths are the minority of losses. Desertion much more commonly came from lack of pay and lack of food. Both of these problems could be more easily solved by finding nice enemy territory to pillage. While armies would revolt over lack of food or lack of pay, doing so is a pretty dicey affair and while you might deride promissary notes as pillage with a receipt, there was much greater restraint by armies using it than those who did straight up pillaging. Further, the big reason to avoid a lot of provisioning efforts at home is because those activities provide an excellent chance to desert.
Another good read is
Conscripts and Deserters, it is fairly clear that desertion gets ever harder the deeper the army goes into enemy territory. Now if you aren't paying your army or if you are fighting at poor odds, desertion increases, but those are not a priori related to how deep you are enemy territory. What does happen as you plunder your way deeper into enemy territory is that you become more hated and deserters are more likely to be killed by vengeful peasants. In home territory you had many more worries about desertion, many more worries about nobles taking issue with your appropriation, and the fact that the officers often had orders to enforce about not pillaging the peasants to the point of starvation.
Going deep into virgin territory simply should not result in more casualties from a historical standpoint. Looking at the journals of people like Marlborough, they never experienced a notable increase in attrition - in spite of jumping off from the Netherlands and going all through Bavaria (enemy territory).
Defense in depth just wasn't a real popular strategy in this era. It was costly, it created all manner of local strongholds for potential rebellions, it expected enemy armies to move deep into home territory (which very rarely happened outside of rebellions). All of the things that make defense in depth effective are much more modern products - things needing to keep close to munition supplies (needs reliance on factory made munitions), home supply of food (needs rail as pointed out by Van Creveld), regular shifting of troops to & from the front (needs rail or motorized transport), fuel supply (mechanization), etc. Defense in depth just doesn't generate major difficulties when you can live off virgin land (as shown by Sherman, Marlborough, Napoleon, etc.).
As far as long bow battles, those were the exceptions insofar as the only major user of this tactic was mainly used by the English. Staked longbows were seen by mercenary companies in Italy and Germany in the previous century, but were falling out of favor by the EUIV period. Nonetheless, we should see at least a few battles where well emplaced elite troops fight in small numbers against superior numbers.
Carpet sieging only occurs because the only thing that really matters to warscore is holding territory. If France wants to take Modena, then it has to siege not just Modena, but a lot of other territory. The historical option of siege Modena, beat back relief, and then take Modena just doesn't give enough warscore. The AI will see its big army as powerful, and the player as not making gains. Yes ticking warscore helps, but that still takes much longer than killing the army and splitting down sieges.
Every buff to the besieger just makes the gains to be had from killing his field army bigger. If I might have sallies, then I REALLY need to kill the field army so I can siege in peace. Now warscore is even harder to get and I will have to detach more of my manpower to get it with sieges. This makes the benefit of killing the field army higher - before I could keep a checking army & say 4 sieges, now I can keep a checking army and say 1-2 sieges. While carpet sieges are more costly, they are relatively much better than a checking army.
Bluntly, if you can't get what you want from the peace table more efficiently than beating down the field army first - players will always beat down the field armies first. If you want competitive AIs they will need to emulate player tactics (e.g. Hunter-Killer stacks), which will mean the AIs also follow ahistorical strategy. If you want historical tactics, you will need to be able to get good return in peace deals without having to first kill the field army. That just isn't possible with the overreliance on sieges for war score.
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I've noticed (some of) the same game mechanics inaccuracies, as far as my knowledge of the period allows and from modding possibilities perspective, adjusting warscore seems to be the cleanest way to go.
