I'm in the UK, but I'm pretty sure the ruling is the same in ROI. If in doubt, check with your local test station.
Yes, for the moment, and untill/unless the EU enforces their proposed tightened regulations on modifying, it's fine to run no airbag provided the warning light is off.
As for insurance, it MUST be declared. If you've disconnected it and haven't told them, don't expect any payout for injury should the worst happen. Some insurers will not cover you if you confess to removing your airbag (for the very reasons you've highlighted) but many will. I rang my insurers before I did the mod to check and they didn't care as long as I told them when I did it (didn't even effect my premium!). I strongly suggest you check your current/future insurer before you buy.
As for the added risk of injury, that's your call