Unprotected during web installation

CIS does an initial scan upon installation. If there is a virus that was picked up, it will let you know. I have yet to experience a virus entering my system from the short time the protection is down. So your argument is invalid.

Unfortunately dropping the firewall protection even briefly can be problematic.
Has it occurred to Comodo that many of us may be preventing things from getting out rather than getting in.

I would suggest changing the web installer to download the required files first, then have it prompt to continue the installation once downloading has completed.
At least then you can choose to drop off-line for the actual install / upgrade.