Dealing with Internal Vacancies - Knock-on effects

Hi all,

Just wondering if there is an obvious answer, best pratice, or IT tool for managing / planning to fill internal vacancies within large teams of similar staff.

Background

I run a team of professional staff.  I have a number of peer managers running similar teams.  Our teams do the same job - we just support different internal customer groups - so people can move between teams quite easily.

Within those teams, there's two tiers of staff - senior and junior.

We always want to give opportunities to internal staff if possible.

Problem I've run into is that when an internal vacancy comes up, there can be a knock-on chain of internal ads, and it wastes an awful lot of time. 

Example

Senior person in my team makes a lateral move to a newly created position.  So I have a senior vacancy.  An internal ad secures me a senior staff member from a peer manager's team.  But that manager now has a vacancy.  We suspect that his vacancy will now be filled by a more junior staff member wanting to "step up".  But that will leave yet another vacancy... and at some point sooner or later, we need to get an external person in to fill the "last vacancy" in the chain.  We just don't know yet where that will be!

Clearly one solution is to just be more autocratic about it, move people around to suit us as a management group, and then advertise externally for wherever the vacancy ends up being.  But that creates simplicity at the expense of transparency. 

Question

Assuming that we do want to keep on being transparent and effectively "advertising" roles so that people can express their interest and make their case, is there any obvious way to minimise the admin involved - eg. IT tool to plan the moves out, hybrid approach where you do some advertising and some dictating? 

My gut instinct is that we are overcooking this process or missing something bleeding obvious as to how you go about this.

Any thoughts / experience / guidance?