Firstly this is experimental and proceed with some degree of experimentation :) 

The big issue with printing ABS/ASA on an non enclosed printer with a bed that cant even reach adequate temperatures is warping.

This simple solution allows you to print ABS without any modifications.

Quite simply all you need to do is print an initial layer of PLA (will test petg as well) and then the rest of the part in ABS.

The pla has a greater bonding force to the bed thus helping eliminate warping, and as a bonus you don't have to have a super hot bed.

Download the profile with a Benchy and you can see I have made a user preset for ABS as Bambu studio won't let you automatically add one by default.

Now by all means this is not perfect I would still keep the print away from drafts and perhaps on parts with a higher warping possibility you could add a brim as well. Also the first layer should be considered sacrificial as the bond between pla and abs is not

I learnt about this trick via JanTec Engineering and I highly suggest you check out his channel on youtube :)