Feeding a sub-panel

[Naptown]

There is no solution I can think of other than a line tap at the house.

[Flint]

Here's the situation:

The house has existing 100A service, into an ancient panel. That's due for replacement, but hopefully it can wait until next year.

There's a new (empty) conduit feeding a new barn, where the inverter will be installed. The current plan is to install a breaker in the house panel and run wiring (250 feet) to the barn. There will be a sub-panel at the barn where the inverter will feed in.

Inverter is rated at 32A continuous output, with a 40A max breaker size. There will be a disconnect and REC meter can between the inverter and the panel.

I would like to be able to add an additional 10kW of PV once the barn is complete (42A continuous, 50A breaker/fuse).

I have a 100A load center (Square D QO120M100RB) to mount on the barn (that's a main breaker panel, but the breaker could be removed and replaced with lugs, if necessary - also, I've heard that there may be lugs which can be installed in the input side of the breaker to allow solar to feed there, without actually flowing through the main?). I also have a HOM48L125GRB sitting around that can be used if there's some benefit. I have two 60A disconnects - one fusible and one not.

My thought was to install a 100A breaker into the sub-panel, connected to the REC meter. I could then install the fusible disconnect with 40A fuses and connect the inverter to that. In the future, I could install a second fusible disconnect and also feed into the supply side of the meter.

However, I don't know if that will be compatible with the 120% / 125% rules (we're using NEC2014, here, according to the inspector) for either the sub-panel or for the main panel. Both currently, and also when the second inverter is installed.

I'd prefer to use the stuff I already have, but since I haven't actually installed it or pulled the wires through the conduit yet, I can still change things if it's necessary.

Any input would be appreciated...