Before I flesh out this topic, could a dev or someone familiar with the code of the game answer the following questions?
- How hard is it to add a new portal with city, guild, and/or settlements as possible destinations?
- Is it possible to have add an option with a variable destination to a portal?
- If yes to the above, can a gatekeeper be modified to change said variable destination?
- Is the game flexible enough to allow for a massive influx of new portals?
As a general idea, if the last three are answered 'yes', I would suggest the creation of a portal and pad combo that can be placed on a plot, and a portal room for dragon lairs. If the second and third points are a 'no', but the other two are plausible, then I would suggest adding a portal and portal room, minus pad, for plot toting convenience.