This thread is getting a bit long since I noticed it the other day, so I've really only skimmed it at this point. But some people seem to think it makes no difference to leave the generator locked during normal use. In my experience, every organ is different enough that blanket statements don't really apply. I've seen organs that are much louder than others when locked but I personnally don't find it acceptable in any case. My current rig has shock mounts installed and even that are noisier than a suspended generator. You can try it both ways, but it only takes two minutes to change.
Also have you been specific about why you want to use the internal speakers? Is it for reverb? I played an a100 for many years with the AO39 tubes pulled and used a leslie. I feel that the static internals clash with the motion and also sound awful by themselves. The reverb is not really anything to write home about, and a 145 is going to sound great all day long by itself. I actually got my a100 for $200 and sold the internal jensens making the organ virtually free. I've never missed them.
General advice on the leslie: always rebuild any leslie amp you get right away, and it's ok to dime it if that's your sound.