In the ACGM there should be a "retired" players list. these would be players that are retired, but still count against the cap. There is opening now that taxi squad is an option. It would also work if shown in typing like for buyouts or buried. Some examples of this are
Marian Hossa
Marian Gaborik
Matt Niskanen

Hossa and Gaborik have an injury history that allows them to go on LTIR and have no affect on the salary cap. Niskanen's cap is forfeit for the season because he retired.

In 99.99% of all cases, LTIR works fine enough for these instances. There are 7 active contracts that would come with cap recapture fees if the player retired today: it's not worthwhile to add. A similar discussion was had in this thread and an identical conclusion was reached.