Yeah, the cost gap shouldn't be an issue when both of their costs are expensive as it is. If you need to intercept something and only have enough UP for a heavy, 99% of the time, you're better off using a soldier (or a valkyrie on DMM, I guess) and an archer instead.

Deploying Gellius and ONLY Gellius for a rush is just setting yourself up for trouble. Gellius/Solano also doesn't outweigh Nadia because of the extra 10 seconds of setup. Unless you put Solano first, in which case, you're still not solving the main problem of actually getting a blocker on the map and you may as well just use a soldier then.