[...]1. I would like to recruit Units generally on a regimental basis - that means that I do not want to recruit complete brigades - instead of this, I would like to recruit every regiment by hand (Infantry, Artillery....)
I think this is possible but quite some work. Take a look to the unit database [font="Courier New"]AACW_DB_Units33d.xls[/font]. The unit database describes the units available in the game. You will find there the information how many and what kind of elements (=regiments) a unit contains. You can create new units in this database which consist only of a single element, these are the ones you want to recruit. After you added your new units you have to save the file as csv and use the CSV-Splitter program to create the necessary unit files.
Now you have to alter the scenario. You have to remove the old units (which consists of several regiments) from the unit pool and replace them with your new single regiment units. You have to check all files connected with the scenario you want to change for the [font="Courier New"]ChangeUnitPool[/font] commands which determine the kind of units (and their quantity) you are able to buy. After that you have to rebuild the scenario (or better create a new one).
If you have further questions regarding the necessary steps don't hesitate to ask, I will post detailed explanations then.