Are there any potential expansion teams?

Hopefully every team that joins the league has ambition for promotion but you'll have some B teams in the league and what if Corks B team wins the league and enters the First Divison but pulls out mid season or at the end of the season because of the costs. If it was me the third tier would be made up of four regional leagues with the four winners playing off for the chance to play for a spot in the first Divison. Can barely keep some of the 20 clubs we have now in business so adding another league of ten teams in a carbon copy league with direct promotion will probably fail.

You're still putting a pyramid system in place just not with direct promotion from the new third tier into the second tier like they do in Scotland with the winners of the highland league and lowland playing off and the winner plays the team that finishes bottom of league 2 in Scotland.

You say that now but if they don't win the league they don't get champions league football and their money for Europe drops quite a bit and if they don't sell on players like they did last season that's less money. There off field costs went up this season and to compete with Dundalk they'll need all funds focused on the senior team. 

What you need is to get the regional senior leagues into the LOI system as a third tier, in time and if the money within LOI improves you can add a new tier and stick it inbetween regional leagues and first Divison.

So you start off with:

Premier Divison  (tier 1)

#direct promotion/relegation and play-off between these tiers

First Divison  (tier 2)

#just a play-off between these tiers

Regional leagues (tier 3) (consists of Munster, Leinster, Ulster, Connaught)

New company is being set up in 2020 to run the league and after its first 3 years of being set up and they increase the money available for league of ireland clubs they can think about adding a fourth tier and set up like this.

The new second Divison (tier 3) can be made of teams who've played in the previous tier 3 (regional leagues) for the first 3 and want to progress up the leagues. Need to walk before you can run and if you tack another ten team league on and it goes bust you're back to square one which will happen if you don't have more money and clubs pull out to go back to their regional senior league.

I think you are over-estimating the level of interest that would be received from the Intermediate Leagues, if you populate Tier 3 with these teams you also have the same problem where all the teams are already in overpopulated LOI cachement areas. It also doesn't do much to serve the problem of players falling away after 19s or the desire of the top teams to have a B side. 

I think the best way to manage this to mandate that every side currently in the underage league has to put in a senior side. On top of this any Junior/Inter side which applies to join will gain access to the national underage leagues (a semi-decent geographical spread should be the target here not Tier 3 full of top DDSl clubs). Finally the opt-in B teams for clubs who wish to join. 

If you got 16 viable teams out of that bunch that would be an incredible start. Split then north/south and have a short season to begin with. Like with the A Championship no reserve side should be allowed promotion. Have a decent play off system with the winner playing the bottom side in the first Division. The long-term aim should be that 1.5 teams are relegated from the first annually.