Interesting reading on this thread. For what it's worth, here are my thoughts....... I think in theory, moving to 10 is a good idea as it gives more teams higher level of football increasing depth - at least that is the idea behind it. In other counties this is the case and some stronger counties will have 12 teams.
In Offaly however, i'd say there are only maybe 6 or 7 proper senior teams at a push at current count. That may change as Clara may return stronger and likes of Ballinagar or Daingean might improve. I can only see Cappincur and Tubber staying as they are or declining with numbers etc even if they were to win a Senior B. In that sense, I think 8 is enough currently but increasing depth to 10 provided teams are improving is only a good idea. However, doing so when teams are not ready, I think is not a good idea. So my summation of it is that the intention is good but the timing is a bit early.
On the structure of that 8 or 10 teams, I will say this. If it is 8 teams, I would go 2 groups of 4 with top team to semi as per current format, next two to q-final and bottom teams in relegation final.
On the two tiers idea, Westmeath have two tiers of 6 in senior A championship - a top 6 and a bottom 6 - each playing 5 games. 4 teams from 6 qualify from top group (2 to semi and 2 to quarter final) with two dropping to second tier following year. From the second tier, the top 2 go to q-final, next two in limbo and bottom 2 play off for relegation. Mostly there is something on the line in most games and you have fairly even contests. It generally works well there and teams have come from second tier to reach semi finals and finals AFAIK.
Could you do similar with 2 groups of 5? Not so sure. There is not much jeopardy in getting out of group if in top tier as 4/5 teams will in this structure, unlike Westmeath where it is 4/6.
Also, The prize of a quarter final place for winning 3 out of 4 games and losing one to group winners could be the same as the prize for drawing one game out of 4 (ie 1pt from

. It is this jeopardy that makes a championship worthwhile and there is certainly a lack of jeopardy in this format which makes a tiered competition for groups of 5 somewhat flawed. We saw last few years how much of a joke it was when the group games had nobody eliminated.
On the reverse of that, there would be good competition if 2/5 teams were going to a quarter in a second tier with possibility of 2 teams up to quarter final, one in limbo and maybe bottom two play relegation final. The difference here with Westmeath is what do they do the following year in terms of who is in the top or second tier. If 4/5 teams in top tier go through, and 2 out of 5 in bottom tier went through, what is the make up of tiers following year? Is it one team up and one down or is it two up and 2 down - which I would have preference for in terms of having flux and reward for doing well in lower tier. What you want to avoid is the rich getting richer and poor getting poorer. If one up one down was implemented between tiers, I think it'd be a big mistake and would only increase gap between higher and lower end of senior A competition.
There is a balance to be got to it all and I wouldnt only be doing this tiered basis of competition because it works for the neighbours. It has to work for the Offaly context for it to be successful and I am not certain it will or won't.
I'd prefer to stay with 8 for now given depth pool but that call has been made already..... they are going to 10. In going to 10, I'd prefer it to be 2 even groups of 5 with top team to semi's, and next two to quarter, team 4 in limbo and 5th teams playing off for relegation. This way, there is likely something riding on every or at least most group games. The top 4 (semi finalists in previous year) teams should be seeded and split to ensure groups are even and also the fixture for the bottom 2/3 teams in each group should be played as the last 2 group games so as no team just packs up after losing to other relegation contenders in early round to keep competition alive for as long as possible for all teams.