If the Penguins were to sign Marner, they could enter next year with this forward group without any additions beyond re-signing Hallander:
Rakell-Crosby-Rust
Bunting-Malkin-Marner
Hallander-Glass-Tomasino
Lizotte-Ponomarev-Acciari
Hayes
Tomasino falls into that "bottom-6 offensive producer" role while their PKers are Ponomarev, Lizotte, Glass, Rust, Acciari and Hallander. They're not really going "youth heavy" in their bottom-6, but the bottom-6 is still fairly young with Acciari being the only guy over 27. In addition it's also very cheap, Glass probably comes in at around $2.5 million again while Hallander and Tomasino probably come in at around $2 million. That bottom-6 is basically just replacing O'Connor, Nieto and Beauvillier with Tomasino, Ponomarev and Hallander.
Honestly I'd even be pretty satisfied with this forward group, it's what they should be doing anyway. Don't spend money on unnecessary bottom-6 forwards, have a few cheap but effective prime aged NHLers surrounded with young guys. It leaves you a bunch of money to address other positions on the roster, namely top-6 C/W and top-4 D.
If you sign Marner for $12.5 million a year and keep the RFAs at reasonable prices, I'm sitting with $7.5 million in cap space with buying out Jarry and having 2 open LD spots (POJ as the 3rd pair RD). The entire McGroarty-Broz-Koivunen line would be starting in WBS, so you have a strong line to call up in case of injuries.