How can I use Unijoy Old Style typing in Ubuntu 14.04?

The post is about Bengali typing using Bijoy Layout in Ubuntu.

Unijoy in Avro is deprecated. But it's still available to use in Ubuntu. As an old school Bijoy layout user, I tend to use the Old Style typing using Avro, but not in Phonetic — using Unijoy, plus the Old Style typing - which is available in Windows still today by some patches.

Recently I became almost a regular user of Ubuntu and I'm using the Unijoy layout beside Phonetic for Bengali typing. But I'm seriously missing the Old Style typing and that affected my typing speed and habit.

I can get into the Setup panel for Unijoy using the dropdown menu, but there's no setting for 'Old Style' or 'Modern Style' there.

Is there any desperate way using the Unijoy Old Style typing with Avro, in Ubuntu?