This idea came into my mind a couple of days ago. It’s just an idea though. All numbers and especially the details of the mechanics can and probably should be changed as needed. Take it as an input to further think about the general concept rather than a finished plan 
Generally the mechanics of both modules is pretty much what the name already says; Combining the Cyno Beacon/Jump Bridge on a POS with the anchoring system of the mobile structures (Mobile Scan Inhibitor or Mobile Depot for example).
The Mobile Cyno Beacon
This mobile structure can be anchored anywhere in your sov space as long as the system has sov level 2. It provides a Cynosural Field, as known, for the alliance of who anchored the structure. Downside is that it will only last 2 hours and explode afterwards. Similar to the Mobile Scan Inhibitor. It should also be destroyable in a moderate amount of time if a small group attacks it. So if you want to keep it up while hostiles are around you need to defend it well.
The Mobile Jump Bridge
For the mobile JB you need your sov level at 3, but can anchor it anywhere in space, too. It only lasts for 2 hours and will be dead after this time. In this timeframe it can be linked to any Cyno Beacon or Cynosural Field that is in range and accessible. There also should be some sort if limit to the mass and/or ships that can use the bridge. It could use fuel like a permanent Jumb Bridge or could have a predefined amount of that. This depends of how much you want to make this a logistical task and/or limit the power of this JB. It should also be killable, but last a little longer than a Mobile Cyno Beacon. Under an attack it should crack in a couple minutes as long as not defended though.
Neither of these should have reinforcement timers or be scoopable. Once deployed they will last the 2 hours or die in a fire - no leftovers.
The idea behind both modules is pretty simple. Having the ability to build up a supply line to a certain area, e.g. a fight, without the need to set up 2 POS or having a titan available. This can help smaller alliances and it might encourage reshipping again, which is sadly pretty uncommun in nowadays EVE. As the Mobile Jump Bridge can also be linked to any cyno on field it might create some interesting scenarios on which a fleet tries to protect it’s cyno - so the JB is not lost - instead of just getting a new one. (Remember, the Mobile Jump Bridge can only be linked to 1 cyno in its lifetime).
The cost of both structures should be moderate, so that it is a strategic decision to use these - but won’t eat up your wallet. Especially the money and the fact that you can’t use these without owning the sov, as well as the rest of it’s mechanics, makes Titan bridges still very viable and won’t replace them.
I do see the chance for small to medium alliances increasing their ability to use infrastructure temporally and a general slight improvement to reach fights and keep them going. On the other hand, it can be useful again to roam around the system a fight is going on in, to find and destroy the enemies supply lines - without the need of getting really big things moved to destroy a complete POS.
Last but not least it might be a possible step between POS and the upcoming structures that will replace the JBs finally.
As said in the beginning, all the numbers and details in the mechanics are just a rough idea. Tell me what you think 
o7