I'm new here so be gentle!

I have been biking on and off for most of my life, even owed a bike shop for several years. This year after dropping 100 lbs I started biking again. I purchased a 2013 Specialized Crossroad this past spring and started riding on area rails to trails. I have really enjoyed the Hybrid and when I owned my shop, which was mostly MTN bikes, I always wanted a hybrid, ie the Specialized. One thing I enjoyed when I had my shop was taking old,tired bikes and upgrading them to useful service again. I did that this summer for a hybrid for my 10 year old granddaughter. I took an old KHS mixte frame and added alloys with 700X28, found a take off Rapid Fire and added a 7 speed hub and derailure. Flat bar w/stem, and a great seat. she rode over 200 miles with me this summer on the Kal-Haven Trail and other rails to trails. I spent $120 on this bike and she loves it.

OK. My question. I now want to build up a bike for myself. I realize there are some great hybrids out there but I like taking old stuff and making it new again. Like to see the results of my efforts. The majority of my riding will be around my home and the rails to trails. Just want a better ride than the Crossroads.

I would like a chrome moly frame, light is good, I like rapid fire shifters, 7 or 8 speed hub, alloy rims 700s and would like to use larger tires like 30 or 32s. What frame should I look for, road or MTB, and I see discussion re; Shimano 105? I have some carpal tunnel in my left hand and someone suggested a carbon fork and handle bar. Not looking to spend much because if I was I would just go buy a new or used hybrid.

Your thoughts and opinions would be appreciated and I hope practical. Thank you.