Hi Chas Ochalek,
While the option to set a subspace as the landing page of a place is not an option in the out of the box platform, there are a couple of options available if you are interested in this type of feature.
Jive Cloud or Custom - If you are interested in seeing this type of feature available in a future release of the Jive platform, I would recommend submitting an idea to the Ideas for Jive space where out Product team pulls from top rated ideas when considering future feature enhancments.
Jive Custom - For a Jive Custom instance, it might also be possible to implement this type of navigate through the use of either a custom theme for your instance or add-on/plugin. If you woudl like to scope out a potential custom option for your instance I would suggest either reaching out to your account manager or submitting a case in your customer group ( MyJive Secret Support Group Administration FAQ ) where a member of our support team can assist in setting up an engagement with our Professional Service's team.