I'm not sure that this is the best way to do it, but I got things working how I wanted them. Here's what I ended up doing:
- Create a new subsite on subsite1 to give me the URL subsite1.ca/subsubsite
- Create a redirect from alias1.tld to subsite1.ca/subsite
- Create 2 pages for the new subsite. One for the default page and one to use to redirect to page2. Both pages are redirects, Default points to Page1, the second points to Page2.
- Set the subsite to use Managed Navigation for global and current through Site Settings > Navigation, and created a default term set by selecting the new subsite in the list and then clicking Create Term Set, then clicking OK.
- Then created a term store for the one page that needs to be handled differently by going to Site Settings > Term Store Management. Click on the Term Set created in the last step, then select New Term. On the Term-Driven Pages tab, create the friendly URL and then select the target page, which is the redirect page created in step 3, then click Save.