Is there any information in Buddhism on mundane mental contemplation (if any)? Is there a benefit for un-concentrated contemplation on a virtuous topic?
Mental contemplation can be useful for training in Morality, but not for training in Concentration or Wisdom. It is good to contemplate your current karmic state, and deduce what actions can be taken or stopped to generate more good karma. That being said, training in Morality is only the first step. Without training in the other two, your chances of becoming free of samsara is very low.
I don't really suggest doing compassion meditation unless you really feel like you generate a lot of bad karma from a lack of compassion. As to weather or not your compassion meditation brings more results than contemplating day to day, only your experience can speak to that.
Contemplation can not replace concentration meditation. Training in concentration is something that requires effort and time for it to be cultivated properly. You can not think your way to stronger concentration skills. You have to actually practice concentrating.
How would a Buddhist fare without formal meditative skills?
Spontaneous enlightenment is possible, but I would not put your chips in that basket if you want to be free this lifetime. All 3 trainings work together in order to help you be free from ignorance, suffering, and samsara. If your goal is to be free, it is essential to pay all three trainings an equal amount of attention. To do that, formal concentration and insight meditation is a must.
It is not possible to think your way to Enlightenment. It is something that must be discovered and felt at the source of your being. At some point you will be required to abandon thought to move further. That can be done easier once you have learned to concentrate, and have found the wisdom present in what you observe.
I hope this was helpful my friend and I wish you nothing but love. 🙏