I'm in the process of structural repairs in my house (with basement shop). The main beam on the first floor is failing, and our design for replacement took into account my intended workflow. I asked my structural engineer about the max span allowed for wooden beams. Not engineered beams, just dimension lumber. He said our code (and I think we adopted the UBC without tweaking this part) requires a vertical support a minimum of every 10 feet for dimension-lumber girders.
We looked at other options and after factoring in cost decided we could arrange the shop around the new posts. But we still went with an LVL to save ourselves a couple of inches of headroom (and at that size, the LVL also required a support every 10 feet.
Whether you need supports closer than that will depend on what you plan to put in the loft, plus the rest of the load. Will the increased load increase your need for rafter ties?
Structural engineers aren't cheap but IMO they're worth it. Specing the 1st floor framing plus a hidden beam in the attic and post footings ran us $750. Given the time and stress for me trying to do it myself, and do it safely, I consider that price a bargain. Plus we're in a jurisdiction that requires permits, and my insurance frowns on DIY repairs without the city's paperwork.
Suggest some professional help, and staying legal if your're in such a place. Also check the insurance fine print for its rules about these changes.