If you´re thinking german players for Liverpool, i would consider players who aren´t at the biggest clubs already and might be looking for a pay raise.
I guess Klopp wants
dominant players, no matter where they come from, so if someone is at Barca (Ter Stegen isn´t dominating, so i´m not talking about him here, alright), Bayern, Juve, PSG,..., there´s no need to go to Liverpool, because at those clubs, they are already 1) earning the biggest money possible and 2) dominating at huge clubs.
So thinking about players like Lewandowski and Müller, Kevin Trapp, Özil,.., i don´t think there´s a big reason (besides the small Klopp connection for some, but he could be gone in an instant) to go to Liverpool.
The best option for german or german-based players would be to pick someone from Dortmund, Schalke, Leverkusen, Gladbach, Augsburg, Mainz, who are playing in Europa League and CL. Those guys would have a reason to go to Liverpool (much more money), might see a connection to Klopp and will come a lot cheaper than those huge sums for guys like Lewandowski.
I don´t think it makes sense to buy someone from Dortmund, as there isn´t anyone there who would be a safe bet to make it at Liverpool (Kagawa, Mikhitaryan had trouble at ManUnited / Dortmund, Reus is an injury waiting to happen, Hummels makes many mistakes, but gets criticized by the fans and might leave soon) or couldn´t help Liverpool for a reasonable price (Aubameyang is running wild, but i don´t know if Liverpool needs another front man, who could come for 75mil.€). The only players i could imagine are Sokratis as defensive depth and Aubameyang if they really want to spend big.
I think it makes more sense to look at other clubs. Who i´m thinking about?
Bernd Leno (Leverkusen, 23, keeper, contract til 18)
Jonathan Tah (Leverkusen, 19, CB, contract til 20)
Sané (Schalke, 19, att.midfield, contract til 19)
Granit Xhaka (Gladbach, 23, def.midfield, contract til 19)
Julian Brandt (Leverkusen, 19, att.midfield, contract til 19)
Klopp doesn´t need superstars and established guys for his system. He needs young players who can run 90minutes with perfect technical ability (also as defenders). If he wants to install a system like at Dortmund, i don´t think he would buy many offensive threats, as there´s already many options.
None of these players has to be sold with only one year remaining, some just came to their clubs or signed new contracts. And if they leave, it will be very expensive (Sané just joined the national team and Julian Brandt will be the next). If he wants to develop some young talent, buy some players like Sané, Tah (just went from Hamburg to Leverkusen for 10mil.€) or Brandt for 20-25mil.€ each, I would guess. Bernd Leno is also on the brink of joining the national team (Weidenfeller just leaving, still too many young keepers rotating behind Neuer) on regular basis and plays in CL basically each season with Leverkusen (150+ Bundesliga matches, 20+CL matches played).
Granit Xhaka led the turnaround at Gladbach this season (started with 6 losses in CL and Bundesliga, then won 8, drew 3 and lost 1 including CL), is a hothead in central midfield, runs around a lot (regularly with high distance/match), has very good technical ability (but lower than Sané and Brandt) and is now captaining Mönchengladbach.
It is rumored he has a 30mil.€ buy-out clause and he was linked several times with Liverpool (and Atletico) already.
If I´m a fantasy GM, I would buy three of those for 80mil.€...