Intra-European Biz class is in most cases simply the same seat as Economy but with a meal and (with many but not all airlines) a blocked middle seat. Given that pretty much no direct intra-Europe flight (with the possible exception of some flights to Istanbul) is much more than ~4:30 hrs duration this is perhaps a reasonable strategy for the airlines.

TAP has a several A321s configured with lie-flat seats which they mostly use between LIS and Northern Brazil (primarily Fortaleza I think). On the inbound from Brazil these sometimes are routed onward to ORY (Paris Orly) for certain, but I'm not sure if they ever go to FCO.

I definitely wouldn't pay for for Biz LIS-FCO at 4x the Economy ticket. 'Fast Track' security at LIS isn't usually worth it in terms of actual minutes saved and the airport is so deficient in terms of available gate space that departing via a Bus gate is a strong likelihood so no proper 'Priority Boarding' as such.

The Lounges at LIS are stupidly overcrowded much of the time, IMO, so I wouldn't buy a premium ticket for the benefit of lounge access.

TL;DR Exit Row Economy is a better use of the OP's funds than Business Class IMHO