No matter how carefully you choose, there is always a chance at gaining nothing during a 4-year term. So, you have a character who is 4 years older with nothing to show for it except, possibly, aging penalties.
The flat skill 1s only appear on rank and event tables, never on the d6 career tables. Unless you roll on personal development for the stat gain chance you'll always get at least one skill (or basic training) in a term.
On the rank tables, they're clearly meant to provide professional minimums without necessarily bumping skills up to superhuman levels. On the event tables, there's no guarantee you're getting a skill to begin with, and when you do they're often providing breadth of skills with something you might not normally get, but again not pushing those extra skills to higher levels.
The mechanic works just fine, you just don't like it. But not liking it doesn't make it broken.
I would have no problem with your house rule in itself, but I'd probably also set a lower term limit if I were using it. It's definitely in that broad category of house rules I don't mind but don't need to see in the core rulebook some day.