That looks like a good idea, I'd give it a try. I think you're right that she needs more A time, just not necessarily all before the first nap. With a short am, long pm routine it is usual to put LO down for the am nap after a shortish A time. The reason for that is it doesn't matter if it's an UT nap as you're going to be waking them anyway. And if you wake LO up after only a short nap with a long A time beforehand, they are likely to be quite grumpy and tired and need their next nap fairly soon afterwards.
So I would do something like:
WU
A 3h
Nap 45 mins (capped)
A 2.5-3h
Nap up to 2h (or up to 1h45 if you prefer)
A 4h
BT
If you start getting pm nap resistance or short napping, you'd probably need to cap the am nap to 30 mins, possibly bringing the pm nap forward just a touch. Welcome to the fun of the 2-1!