Kai, I did consider the negative aspects with my post, but if you review the type of posts U (Kaz) has been posting, its obvious he's playing with things he doesn't understand and may have a safety impact on himself and others. Playing with micros, the worst case outcome is usually a bit of smoke and most likely it doesn't work.
We all have to start somewhere, but as we get older we hopefully learn how 'learn' rather than just brute force. You can keep on hitting things hard and eventually they'll break - at some point you have to stop and investigate a more efficient means of breaking things! This is my point to the OP - do a bit of reading and get a bit of a background and get the help of someone more knowlegable. One can consider the internet a source of knowlege - a willing audience of skilled people ready to answer questions - hell, I could make an atomic bomb from information from the internet and I'm sure there's plenty of people that have experience in making these things - does that mean they should endorse my endeavours? If I started asking questions about what happens if I get too much fissionable material in close proximity, you'd have to think I was playing with stuff I had no idea of and that for everybody's sake I should refrain.

To U Kaz, remember everything in this life is less than perfect - things do not happen instantly. Motors take time to accelerate and time to decellerate, relays take a finite time to operate, your PLC takes a finite time to do its stuff. Whether or not these times are significant to your application is the question. One could say though, the relay is going to operate faster than your motor and at a guess, your shortcut of combining brake and motor control off one output may be the critical issue. You might just need to 'bite the bullet' and get a larger PLC. Many times I've seen a problem 'patched' up, then another 'patch' on top of that and so on. You end up with something that 'works' but pity help anyone who has to fix it! Done properly, your PLC code would have a comment like 'stop motor', 'wait xx mS for motor to slow down', 'release brake on motor Y'. If anyone needs to change any of this in the future, you've given them a hint on what to look out for. If ever you find yourself of applying a 'fix' then having to apply another 'fix' then stop and re-evaluate the problem.