In all honesty, I don‘t think anyone has about a replacement other then mothballing the 109.
What we need is a 155 for heavier longer range support (weight of fire), and a 105 for closer direct support (speed of fire). MLRs would be nice for CB (but a pipe dream).
Tracked are gone so that leaves either wheeled or towed. Wheeled are nice, but heavier and more expensive. And anyway, I think a wheeled 105 a waste of money because you can get light wieght towed 105s.
The C3 is already in place, so that‘s is probably the way we wil go (or stay). However, the British Light Gun or US M101 would be perfect for 105s.They are light weight, 6400 mils travesable, and transportable. And there is no change in ammunition.
For 155, the one that makes the most sense is the American M198 in service now. Unfotunatly it is towed, but budget restraints would force us down this route. The best option for wheeled, I think is the South African G6, but purchase costs rule this out.
In the end, the cutting of the M109 is to save costs, and nobody has looked at the cost/benfit of purchasing a new 155 system. So in the end you will probaly see a mixture of 105 and 81mm motars in keeping with our peacekeeping and cost saving image.