I don't think I would want to relocate the batteries and propane tanks. You won't find a SAFER place to have these units on your TT. Moving the Batteries and Propane to the inside of the trailer if you had room would require proper venting and fluid retention from batteries boiling out or spills etc. Rerouting of battery cable wiring and propane lines would be another headache to contend with.
I'm thinking you can mount a metal battery box like this 48-inch side mount tool box between your propane tanks and the front wall of the trailer.
Looks like you have plenty of room with your 2013 Sport trex to do this...
Photo from GOOGLE IMAGES
The BATTERY BOX would look something like this. This style metal box will hold four each GC2 6VDC Golf cart batteries. The metal battery box will add thief security for your batteries.
Photo from GILLDAWG79
I believe you will be able to mount many bicycles over the top of the battery box using the appropriate bike mounting kits. The bicycle mount will use the trailer frame for primary support.. You should be able to extend the bicycle mount out over the top of the propane tanks and run a support frame from the front end of the tongue area as well. Three bicycles are shown here. You may have to engineer a hinge arrangement near the the front of the trailer so once you remove the bicycles you can hinge up the frame to gain access to the battery box and propane tanks.
Photo from GOOGLE IMAGES
Maybe four main supports from the trailer frame going up from both side of the PROPANE TANKS would be sufficient to hold the bicycle rack for six units. The rack would extend back toward the front of the trailer as well forward over the top of the propane tank... You can have a few different solutions here to support the bicycle frame from the trailer tongue area.
Just some of my thoughts here...
Roy Ken
My Posts are IMHO based on my experiences - Words in CAPS does not mean I am shouting
Roy - Carolyn
RETIRED DOAF/DON/DOD/CONTR RADIO TECH (42yrs)
K9PHT (Since 1957) 146.52M
2010 F150, 5.4,3:73 Gears,SCab
2008 Starcraft 14RT EU2000i GEN
2005 Flagstaff 8528RESS