Peter Ruddick
Hello A few points Find a structural engineer that understands timber frame alterations, timber frames flex and settle - a little , brick and steel do not . You have to be very careful not to cut out any of the designed in stability of the 'Box' for want of a better description . You may be able to use a Gluelam type wood beam with a structural up stand in timber , but it would need to be braced and designed into the original design , not easy . Looks like your design is for an independent beam and support inside the timber frame , lateral stability would be an issue as it may be independent from the timber frame . Any new supports would need to be off the actual foundations,[ or wall ] not any concrete floor slab or oversite . What ever you do have it signed off / inspected/ by Building Control and your engineer before it is covered up ! I worked for Barratt Homes building lots of timber frames in the 70/80s Good luck Peter R. Beamish Const Services