If the game were realistic you should be getting a lot of heat for signing an unscouted player. And if he doesn't perform well you should probably get the boot. Alas, I don't think the game is coded like that so you'll have to impose this level of realism on yourself by not signing them in the first place.
The guidelines aren't some random restrictions people made up after one brainstorm, but have evolved over many years and thousands of LLM careers. Of course you can go ahead and argue every single one of them on some basis, and "realism" is always brought forward as the number one argument why it should be ok to bend the rules, but just because you can find an exception to the general practice in real life doesn't mean this makes a guideline irrelevant.
The game doesn't simulate real life 100% (yet) and all of the guidelines are designed in a way to maximize realism and fun, within the constraints of the game. As the game evolves, so do the guidelines, but they do so slowly. Stick to them 100% and you are guaranteed a fairly realistic and fun long-term experience.
Linear Mode
