I'm not sure how it would get abused or how it would be any different to a side now focusing on cup games when they have nothing to play for in the League. Unless you were one of the top 10 ranked sides then nobody will be guaranteed anything until the final round or two of the season. And teams focusing on one competition over another is nothing new - I can recall Liverpool fielding weakened sides at the end of the 06/07 and 17/18 season when they had little to nothing to play for in the League but were on their way to CL finals.Correct in that case neither team should get a place, I actually think these extra CL places should be going to champions of smaller leagues, but I used that example to show how silly it is.
StumbleBum said it all really, he explained in a nutshell how it will get abused.
And I disagree on giving more places to smaller Leagues. A lot of people might not want to admit to it but nobody wants to or will watch Bayern beat Neftci from Azerbaijan 6-1, many more would watch Bayern play Roma or Ajax. Imo there's already enough spaces for teams from smaller nations and they're getting an extra two from this proposed change - any sides good enough to be in the CL will make their way into the CL through the qualification rounds. If they can't get through the qualifiers then they probably aren't good enough for the real thing.