In Jain Dharma, bhav shuddhi and sacchai of worship are more important than perfection of direction.

If the north-east is not possible, you can still do the following with devotion:

• Keep the place clean, शांत, and sacred
• Choose the most undisturbed and respectful area available
• Keep the idol/derasar area simple and uncluttered
• While doing darshan, puja, or swadhyay, try to face east or north if possible
• Avoid placing the shrine near toilet, kitchen heat, or dirty areas
• Maintain regular daily puja, prarthana, and samayik with sincere bhavna

In Jain tradition, the intention, purity, and discipline of the worshipper matter greatly. So if south-west is your only option, do not worry too much—make it as clean and respectful as possible, and focus on devotion to the Tirthankars.

If you want, I can also give you a simple Jain home mandir setup for a south-west space.