Dense index?

While looking into pg_filedump output of int4 btree index, It strikes
me that in leaf pages about 25% of page is wasted because of 8 byte
alignment (MAXALIGN on 64bit architecture): an index tuple consists of
8 byte tuple header + 4 byte key + 4 byte alignment, thus 4/(8+4+4) =
25% is waste.

I know that the alignment is required for faster memory access, but
sometimes we may want to save disk space for index to save I/O because
these days customers want to handle huge number of rows. To make index
more "dense", can we add an option something like "dense index" to
align index tuples by using INTALIGN rather than MAXALIGN?

I feel like this had been discussed before but I couldn't find the
discussion.

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp