The games becomes demanding the moment you step into the power-player realm. Normal players will log 2-3 times a day for 5 mins at max. Once to prepare for match, once to set up transfers and training, last one if they play 2 matches a day. I myself have a second account in league 2 which i log just once a day to assign skill points and prepare the field for next match. No token farming there, no power leveling, nothing at all. Yet, with logging once a day i can easily be 1st with a mediocre team after all, qualified in CL group, passed even the cup qualifiers and about to win the leg too.

This game ain't demanding at all. It's the way players decide to play it making it so. If it's too much, instead of freezing, just slow down. It isn't written anywhere that to make a season your quality should be over 10-15 points the opponents, as it isn't written anywhere that you can't miss a match, lose a game, get out of a competition or don't make no.1 for a month.

On the tecnical side, what you justly describe as easy, would be a programmer's pain in the ass. You would have to reorganize the whole server, every server, to take out teams deciding to freeze, resulting in seasons with less than 14 teams in the league, resulting in having to manually (you can't script it as it varies on how many players in which one server freezes team) promote/demote teams to balance it out, resulting in going to either favour or penalize other players who shouldn't be involved in your pace or will to play or not.

I play online since 2001 and never once i heard or seen about preserving your goodies intact while being away. In every game so far quitting for X days or months means having to catch up later. While in a mmorpg you have to skip sleep to do so (powerleveling back, questing, dungeons, and so on) and kill your brain to requip up to the current best in game, in top eleven all you needa do is buy few tokens, rebuild a competitive team with scouts/markets, and after one season you're back to the point.