Since rebranding the European Cup to become the Champions League, the size and value of Europe's premier club competition has grown rapidly.

With that growth there has been significant change, and calls for further evolution, with the clubs at the top of the game becoming distanced from the rest.

What benefits the few isn't always good for the rest and concerns from clubs worried they'll suffer in the long term have become louder in recent years.

Now Celtic and a group of similar-minded clubs from across the continent have taken steps to push for a change that could be significant for European football.

STV has has taken a look at what could happen if UEFA and its clubs are persuaded a major overhaul is needed.

The club, along with representatives of other clubs from smaller nations, met with UEFA this month to suggest and lobby for an expansion of the Champions League. They want the group stage to be expanded to 48 teams from the current 32.

As Scottish champions for the last five seasons, Celtic have reached the group stage of the Champions League on three occasions but want a route for clubs on a regular basis. That feeling is shared by clubs across the continent, particularly in the Netherlands, Portugal and in Scandinavia.

There is a very real fear from some clubs across Europe that changes already introduced are the next step on the road to a 'closed shop' Champions League that is just for the richest of the rich.

Without access to Champions League money, the gap between rich and poor would widen and there have been warnings that domestic leagues would suffer a knock-on effect.

"The threat is very real, very significant," SPFL chief executive Neil Doncaster said last year.

"It is important to be a domestic champion club, that is the same across Europe, it is about access to the top-tier of European competitive football with the other champions of European football.

"Remove that and you fundamentally remove what is important about being a champion in a domestic contest. You would damage irreversibly the mid-level domestic leagues."

As part of a major shake-up of the competition, Scotland's champions will face four qualifying rounds before making the group stage for the three seasons from 2018/19.

This is part of the move to accommodate the top four teams from the four biggest leagues - England, Spain, Germany and Italy - in the group stage for the next competition cycle. That's half of the available places in the group stage taken up from just four leagues.

The aim is to find a model that benefits everyone. Preserving a place in the Champions League for the winners of championships outside the bigger nations is the prime objective.

However, it stands little chance of success if it can't also deliver positives for the bigger clubs and for UEFA itself. That means revenue increases for both.

There are already some who see the group stage of the competition as suffering from a lack of competition and the same few big sides make it through every year. Each season sees at least one hammering being handed out from a Goliath to a David and the inclusion of smaller teams being questioned.

That leads to concerns about viewing figures for the competition ongoing, at least in the early stages and whether broadcast revenues and sponsorship will continue to rise.

When this debate takes place, it is never about the attractiveness of Manchester City v Juventus but always a team from outwith the big four whose right to play at elite level is called into doubt. Real Madrid's disdain for a match against BATE Borisov in 2008 is a prime example.

A new proposal to reshape the tournament to the advantage of the middle tier has to address those concerns head on.

We don't know what detail Celtic and their colleagues put to UEFA but there are many ways to reformat the competition for more teams. We've looked at two of the more obvious possibilities.

Any call for a 48-team Champions League instantly brings to mind the changes recently announced to the World Cup, which will increase to the same number of teams from 2026.

That model seems like an obvious template to look at but it also has obvious flaws.

The World Cup is to begin with 16 groups of three and looking at that from the perspective of European football, it seems very neat.

Sixteen groups could mean a top seed place for the top four sides from the top four leagues, instantly offering the biggest clubs stature and protection. The remaining 32 sides could be split by their club coefficient into two seeding groups.

The number of group stage games would be same as it is currently, with 96 games played between September and December.

The format could also allow some flexibility for the knockout rounds. Allowing the top team from each group through would mean a round of 16, as the competition currently has.

Alternatively, two could go through per group with an additional last 32 knockout round added.

The major problem here is that a group of three means one team sitting out per matchday. That creates a difficult calendar and poses a real problem with the final group of games when two sides may be able to play out a draw to knock out the third.

If that could be overcome there are both pros and cons for the bigger sides. Automatic seeding and avoiding another 'Big Four' side increases chances of progression. However, with less teams and games in the group, one slip could be more costly than it is at the moment, where there are another five games to prove superiority.

Far simpler would be to take the existing Champions League model and add four more groups of four.

This would increase the number of games significantly. There would be 144 games in the group stage, which might risk saturating the market, though individual teams wouldn't face any more matches than they do at the moment.

That increase in games could help drive up revenues for UEFA and result in a bigger pot to split between clubs.

The champions of the top 12 leagues could all be made top seeds and kept apart with others being seeded according to club coefficient.

There would also be flexibility over whether to add an extra knock-out round.

To create a round of 16, the group winners plus the four best second-placed teams would qualify. If a round of 32 is preferred then the top two sides in each group, plus the eight best third-placed teams would progress.

One consolation in the current set-up is that middle-tier teams can at least rely on the Europa League as a secondary competition. Either because they fail to make the Champions League groups or finish third and drop into the Europa after Christmas, it provides additional competition and revenue.

A Europa League that 'loses' another 16 teams to its big brother might struggle for profile and the impact on the secondary competition would probably be a factor in any changes.