It would be interesting if Nordeus changed the cup format so that it was a competition between all of the teams within 8 leagues. (This would make it more similar to the cups around the world...since they are between all of the teams within top leagues of that country).

In order to make it work, a few things would have to happen.

First, increase the number of teams in the league to 16 teams. This would allow 8 leagues of 16 teams to be grouped within the cup. Take the top 8 leagues and place them in the same cup and keep going down until you have 8 level 2 teams in the same cup. The cup will still stay the same 128 teams.

Second, the extra 2 teams in the league will cause the season to need 4 more league games. They can be placed within the current schedule of games on Day 1, 2, 20 and 28. And since the league is bigger, the top 8 will be promoted each season.

A possible schedule could look like:
01 Cup Pre-1 League 01-1
02 Cup Pre-2 League 02-1
03 Champ G-1 League 03-1
04 Cup Q-1 League 04-1
05 Champ G-2 League 05-1
06 Cup Q-2 League 06-1
07 Champ G-3 League 07-1
08 Cup Play-1 League 08-1
09 Champ G-4 League 09-1
10 Cup Play-2 League 10-1
11 Champ G-5 League 11-1
12 Cup T16-1 League 12-1
13 Champ G-6 League 13-1
14 Cup T16-2 League 14-1
15 Champ R16-1 League 15-1
16 League 01-2 League 02-2
17 Champ R16-2 League 03-2
18 Cup QF-1 League 04-2
19 Champ QF-1 League 05-2
20 Cup QF-2 League 06-2
21 Champ QF-2 League 07-2
22 Cup SF-1 League 08-2
23 Champ SF-1 League 09-2
24 Cup SF-2 League 10-2
25 Champ SF-2 League 11-2
26 Cup F League 12-2
27 Champ F League 13-2
28 League 14-2 League 15-2

I made Day 16 the day with 2 league games instead of day 20 since it was at the half way point of the season.

Since the cup would be based on the teams within the league, the leagues would have to be determined before the cup draw. So, the first league game could be on day 1.