Only because of Strange Eons is such a thing possible, but I was considering making an expansion board for when an investigator is lost in time and space. Rather than be delayed and lose a turn while chilling near the sky and outskirts, they go to a small expansion board. They could be hurled back to the Hyborian Age where they travel about Cimmeria, Stygia Aquilonia, etc. They get a random task or mission card and must go to several locations in order to return to the present (as well as get a payoff for the hard work). Monsters would spawn in different areas based on the movement symbol displayed on the drawn Mythos card, and there is a great opportunity for drawing magical weapons and spells while undergoing encounters there. The map would be the continent of Hyperboria, and the encounter cards would elaborate that several months or even years go by every turn, so basically the character comes back after a longer time than experienced by the other characters (where each turn is a day).
Other maps could be during the heyday of the roman empire, the european dark ages, the Arabian Islamic golden age, american civil war, or the distant future where deep ones have humanity on the verge of extinction, not to mention world war ii. Declaring the use of this option would count as using one of the expansion boards, so you deduct one from the total number of players when calculating monster limits, outskirts limit, and portal victory/loss conditions. Should a character be trapped in another era when the ancient one is awakened, they would still participate in the final battle as if they were in arkham (let's not forget that the ancient ones don't conform to our three dimensions and euclidian physics)
some ideas floating around in my head are allies that are easily gained in the past (or future) and are very powerful, but do not follow you back to the present (1926) when you complete the task card, though you may keep any other items or skills gained. Any monsters in your location when you succeed at the task come back with you to the present. Each board or particular areas of a board have their own environment permanently printed on the board itself (kinda like the sneak modifiers on the innsmouth board), so they ignore the Arkham environments but have their own thing (like in Stygia or golden age arabia you have sand storms that deal stamina damage in open areas just as ithaqua's icy wind). past eras would permit limited draws (example: search through the unique items deck, starting from the top card, and take the first magical weapon you come across), future eras would require me to make new items on my own that can only be drawn while in that future era. it would also require the injury and madness cards from the dunwich horror expansion, since there is no asylum or hospital to fall back on to cure your ailments. each board would have 3-4 open areas, and 6-9 locations.
What do you guys think. Any tips or suggestions before I put mouse pointer to text box?