The home built ones I have seen share a common trait. They are HEAVY. It seems that everyone doing it wants to build a better TT than what is mass produced. In doing so they end up heavy... That is the challenge that the manufacturers face . Balancing weight vs cost vs. what it can be towed with.
Nothing wrong with building a heavy TT, so long as you are prepared for it.
Start with the running gear on the frame you have now. Upgrade the axles/springs and beef up the frame to way more than you think you will need...You most likely will need it.
When it is done, be prepared to have a STOUT TV for it... Not one of todays 1/2 tons on steroids.