Doesn't have to be so tedious. If you have a list of URLs you can use the bulk removal extension for Chrome found here: https://github.com/noitcudni/google-webmaster-tools-bulk-url-removal

If you are going to expand further on each service, then it makes sense to break it down further and use a blurb on the main services page for each. Google what is called a silo site structure for more information.

I agree that this is a great idea, when handled properly.

Oleg pretty much covered everything but this 2013 post from SEORoundTable.com covers this tactic as well: http://www.seroundtable.com/competitor-domain-name-17032.html

Definitely a duplication issue as they are 2 different pages.  Pick one way and stick to it, probably remove is the easiest.  I would do redirects first, but set canonical as well as a best practice.  There is a great guide here:

http://www.kodecreations.co.uk/google/remove-trailing-slash-magento-urls-duplicate-content-issue/

It even includes instructions on how to stop Magento from generating urls with trailing slashes.

As the parent company, I would want any individual work done to benefit the main site and as a store owner, I would want to have some benefit from the parent company as well. There need to be policies in place to prevent bad practices, but it should be all stores and the parent company helping each other. If they want to be treated as a separate entity then they should probably build a website themselves on a separate domain. Most major retailers have the stores in subfolders. Go check walmart.com as an example.